International Nuclear Information System (INIS)
Hasenfratz, P.
1983-01-01
The author presents a general introduction to lattice gauge theories and discusses non-perturbative methods in the gauge sector. He then shows how the lattice works in obtaining the string tension in SU(2). Lattice QCD at finite physical temperature is discussed. Universality tests in SU(2) lattice QCD are presented. SU(3) pure gauge theory is briefly dealt with. Finally, fermions on the lattice are considered. (Auth.)
Hadron structure from lattice QCD
International Nuclear Information System (INIS)
Schaefer, Andreas
2008-01-01
Some elements and current developments of lattice QCD are reviewed, with special emphasis on hadron structure observables. In principle, high precision experimental and lattice data provide nowadays a very detailled picture of the internal structure of hadrons. However, to relate both, a very good controle of perturbative QCD is needed in many cases. Finally chiral perturbation theory is extremely helpful to boost the precision of lattice calculations. The mutual need and benefit of all four elements: experiment, lattice QCD, perturbative QCD and chiral perturbation theory is the main topic of this review
Improved methods for the study of hadronic physics from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Orginos, Kostas [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Richards, David [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2015-02-05
The solution of QCD on a lattice provides a first-principles method for understanding QCD in the low-energy regime, and is thus an essential tool for nuclear physics. The generation of gauge configurations, the starting point for lattice calculations, requires the most powerful leadership-class computers available. However, to fully exploit such leadership-class computing requires increasingly sophisticated methods for obtaining physics observables from the underlying gauge ensembles. In this study, we describe a variety of recent methods that have been used to advance our understanding of the spectrum and structure of hadrons through lattice QCD.
International Nuclear Information System (INIS)
Shindler, A.
2007-07-01
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-07-15
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Multi-Quarks and Two-Baryon Interaction in Lattice QCD
International Nuclear Information System (INIS)
Okiharu, F.; Suganuma, H.; Takahashi, T. T.; Doi, T.
2006-01-01
We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-quark potentials in lattice QCD to clarify the inter-quark interaction in multi-quark systems. We find that all the multi-quark potentials are well described by the OGE Coulomb plus multi-Y-type linear potential, i.e., the multi-Y Ansatz. For multi-quark systems, we observe lattice QCD evidences of 'flip-flop', i.e., flux-tube recombination. These lattice QCD studies give an important bridge between elementary particle physics and nuclear physics
Lattice QCD: Status and Prospect
International Nuclear Information System (INIS)
Ukawa, Akira
2006-01-01
A brief review is given of the current status and near-future prospect of lattice QCD studies of the Standard Model. After summarizing a bit of history, we describe current attempts toward inclusion of dynamical up, down and strange quarks. Recent results on the light hadron mass spectrum as well as those on the heavy quark quantities are described. Recent work on lattice pentaquark search is summarized. We touch upon the PACS-CS Project for building our next machine for lattice QCD, and conclude with a summary of computer situation and the physics possibilities over the next several years
Lattice and Phase Diagram in QCD
International Nuclear Information System (INIS)
Lombardo, Maria Paola
2008-01-01
Model calculations have produced a number of very interesting expectations for the QCD Phase Diagram, and the task of a lattice calculations is to put these studies on a quantitative grounds. I will give an overview of the current status of the lattice analysis of the QCD phase diagram, from the quantitative results of mature calculations at zero and small baryochemical potential, to the exploratory studies of the colder, denser phase.
Scattering processes and resonances from lattice QCD
Briceño, Raúl A.; Dudek, Jozef J.; Young, Ross D.
2018-04-01
The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This article reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.
Nucleon structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Dinter, Simon
2012-11-13
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.
Nucleon structure from lattice QCD
International Nuclear Information System (INIS)
Dinter, Simon
2012-01-01
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a 2 ) discretization effects.
International Nuclear Information System (INIS)
Jansen, K.; Michael, C.; Urbach, C.
2008-04-01
We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. With N f =2 flavours of light quark, this is the so-called η 2 meson and we discuss the phenomenological status of this. Using maximally twisted-mass lattice QCD, we extract the mass of the η 2 meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses. (orig.)
Disconnected Diagrams in Lattice QCD
Gambhir, Arjun Singh
of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.
Disconnected Diagrams in Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gambhir, Arjun [College of William and Mary, Williamsburg, VA (United States)
2017-08-01
of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.
Chiral perturbation theory for lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Baer, Oliver
2010-07-21
The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)
Chiral perturbation theory for lattice QCD
International Nuclear Information System (INIS)
Baer, Oliver
2010-01-01
The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)
Aoki, Sinya
2013-07-01
We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for nucleon-nucleon potentials.
Lattice QCD. A critical status report
Energy Technology Data Exchange (ETDEWEB)
Jansen, Karl
2008-10-15
The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)
Lattice QCD. A critical status report
International Nuclear Information System (INIS)
Jansen, Karl
2008-10-01
The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)
Improved methods for the study of hadronic physics from lattice QCD
International Nuclear Information System (INIS)
Orginos, Kostas; Richards, David
2015-01-01
The solution of quantum chromodynamics (QCD) on a lattice provides a first-principles method for understanding QCD in the low-energy regime, and is thus an essential tool for nuclear physics. The generation of gauge configurations, the starting point for lattice calculations, requires the most powerful leadership-class computers available. However, to fully exploit such leadership-class computing requires increasingly sophisticated methods for obtaining physics observables from the underlying gauge ensembles. In this paper, we describe a variety of recent methods that have been used to advance our understanding of the spectrum and structure of hadrons through lattice QCD. (paper)
Topology in dynamical lattice QCD simulations
International Nuclear Information System (INIS)
Gruber, Florian
2012-01-01
Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.
Topology in dynamical lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Gruber, Florian
2012-08-20
Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.
International Nuclear Information System (INIS)
Borsanyi, Sz.; Kampert, K.H.; Fodor, Z.; Forschungszentrum Juelich; Eoetvoes Univ., Budapest
2016-06-01
We present a full result for the equation of state (EoS) in 2+1+1 (up/down, strange and charm quarks are present) flavour lattice QCD. We extend this analysis and give the equation of state in 2+1+1+1 flavour QCD. In order to describe the evolution of the universe from temperatures several hundreds of GeV to the MeV scale we also include the known effects of the electroweak theory and give the effective degree of freedoms. As another application of lattice QCD we calculate the topological susceptibility (χ) up to the few GeV temperature region. These two results, EoS and χ, can be used to predict the dark matter axion's mass in the post-inflation scenario and/or give the relationship between the axion's mass and the universal axionic angle, which acts as a initial condition of our universe.
International Nuclear Information System (INIS)
Woloshyn, R.M.
1988-03-01
The basic concepts of the Lagrangian formulation of lattice field theory are discussed. The Wilson and staggered schemes for dealing with fermions on the lattice are described. Some recent results for hadron masses and vector and axial vector current matrix elements in lattice QCD are reviewed. (Author) (118 refs., 16 figs.)
Lattice QCD for Baryon Rich Matter – Beyond Taylor Expansions
Energy Technology Data Exchange (ETDEWEB)
Bornyakov, V. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Boyda, D. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Goy, V. [School of Natural Sciences, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Molochkov, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Nakamura, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki, Osaka, 567-0047 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198 (Japan); Nikolaev, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Zakharov, V.I. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Moscow Inst Phys & Technol, Dolgoprudny, Moscow Region, 141700 (Russian Federation)
2016-12-15
We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.
Lattice QCD for Baryon Rich Matter – Beyond Taylor Expansions
International Nuclear Information System (INIS)
Bornyakov, V.; Boyda, D.; Goy, V.; Molochkov, A.; Nakamura, A.; Nikolaev, A.; Zakharov, V.I.
2016-01-01
We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.
Comparative Study of Algorithms for the Numerical Simulation of Lattice QCD
International Nuclear Information System (INIS)
Luz, Fernando H. P.; Mendes, Tereza
2010-01-01
Large-scale numerical simulations are the prime method for a nonperturbative study of QCD from first principles. Although the lattice simulation of the pure-gauge (or quenched-QCD) case may be performed very efficiently on parallel machines, there are several additional difficulties in the simulation of the full-QCD case, i.e. when dynamical quark effects are taken into account. We discuss the main aspects of full-QCD simulations, describing the most common algorithms. We present a comparative analysis of performance for two versions of the hybrid Monte Carlo method (the so-called R and RHMC algorithms), as provided in the MILC software package. We consider two degenerate flavors of light quarks in the staggered formulation, having in mind the case of finite-temperature QCD.
International Nuclear Information System (INIS)
DeGrand, T.
1997-01-01
These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and α s (M z ), and B-anti B mixing. 67 refs., 36 figs
Full CKM matrix with lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Okamoto, Masataka; /Fermilab
2004-12-01
The authors show that it is now possible to fully determine the CKM matrix, for the first time, using lattice QCD. |V{sub cd}|, |V{sub cs}|, |V{sub ub}|, |V{sub cb}| and |V{sub us}| are, respectively, directly determined with the lattice results for form factors of semileptonic D {yields} {pi}lv, D {yields} Klv, B {yields} {pi}lv, B {yields} Dlv and K {yields} {pi}lv decays. The error from the quenched approximation is removed by using the MILC unquenced lattice gauge configurations, where the effect of u, d and s quarks is included. The error from the ''chiral'' extrapolation (m{sub l} {yields} m{sub ud}) is greatly reduced by using improved staggered quarks. The accuracy is comparable to that of the Particle Data Group averages. In addition, |V{sub ud}|, |V{sub ts}|, |V{sub ts}| and |V{sub td}| are determined by using unitarity of the CKM matrix and the experimental result for sin (2{beta}). In this way, they obtain all 9 CKM matrix elements, where the only theoretical input is lattice QCD. They also obtain all the Wolfenstein parameters, for the first time, using lattice QCD.
International Nuclear Information System (INIS)
Christ, Norman H
2000-01-01
The architecture and capabilities of the computers currently in use for large-scale lattice QCD calculations are described and compared. Based on this present experience, possible future directions are discussed
Energy Technology Data Exchange (ETDEWEB)
DeGrand, T. [Univ. of Colorado, Boulder, CO (United States). Dept. of Physics
1997-06-01
These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.
International Nuclear Information System (INIS)
Sternbeck, A.
2006-01-01
Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator. (orig.)
Two-color lattice QCD with staggered quarks
Energy Technology Data Exchange (ETDEWEB)
Scheffler, David
2015-07-20
The study of quantum chromodynamics (QCD) at finite temperature and density provides important contributions to the understanding of strong-interaction matter as it is present e.g. in nuclear matter and in neutron stars or as produced in heavy-ion collision experiments. Lattice QCD is a non-perturbative approach, where equations of motion for quarks and gluons are discretized on a finite space-time lattice. The method successfully describes the behavior of QCD in the vacuum and at finite temperature, however it cannot be applied to finite baryon density due to the fermion sign problem. Various QCD-like theories, that offer to draw conclusions about QCD, allow simulations also at finite densities. In this work we investigate two-color QCD as a popular example of a QCD-like theory free from the sign problem with methods from lattice gauge theory. For the generation of gauge configurations with two dynamical quark flavors in the staggered formalism with the ''rooting trick'' we apply the Rational Hybrid Monte Carlo (RHMC) algorithm. We carry out essential preparatory work for future simulations at finite density. As a start, we concentrate on the calculation of the effective potential for the Polyakov loop, which is an order parameter for the confinement-deconfinement transition, in dependence of the temperature and quark mass. It serves as an important input for effective models of QCD. We obtain the effective potential via the histogram method from local distributions of the Polyakov loop. To study the influence of dynamical quarks on gluonic observables, the simulations are performed with large quark masses and are compared to calculations in the pure gauge theory. In the second part of the thesis we examine aspects of the chiral phase transition along the temperature axis. The symmetry group of chiral symmetry in two-color QCD is enlarged to SU(2N{sub f}). Discretized two-color QCD in the staggered formalism exhibits a chiral symmetry breaking
Innovations in lattice QCD algorithms
International Nuclear Information System (INIS)
Orginos, Konstantinos
2006-01-01
Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today
Lattice QCD production on commodity clusters at Fermilab
International Nuclear Information System (INIS)
Holmgren, D.
2003-01-01
We describe the construction and results to date of Fermilab's three Myrinet-networked lattice QCD production clusters (an 80-node dual Pentium III cluster, a 48-node dual Xeon cluster, and a 128-node dual Xeon cluster). We examine a number of aspects of performance of the MILC lattice QCD code running on these clusters
Multi-meson systems in lattice QCD / Many-body QCD
Energy Technology Data Exchange (ETDEWEB)
Detmold, William [College of William and Mary, Williamsburg, VA (United States)
2013-08-31
Nuclear physics entails the study of the properties and interactions of hadrons, such as the proton and neutron, and atomic nuclei and it is central to our understanding of our world at the smallest scales. The underlying basis for nuclear physics is provided by the Standard Model of particle physics which describes how matter interacts through the strong, electromagnetic and weak (electroweak) forces. This theory was developed in the 1970s and provides an extremely successful description of our world at the most fundamental level to which it has been probed. The Standard Model has been, and continues to be, subject to stringent tests at particle accelerators around the world, so far passing without blemish. However, at the relatively low energies that are relevant for nuclear physics, calculations involving the strong interaction, governed by the equations of Quantum Chromodynamics (QCD), are enormously challenging, and to date, the only systematic way to perform them is numerically, using a framework known as lattice QCD (LQCD). In this approach, one discretizes space-time and numerically solves the equations of QCD on a space-time lattice; for realistic calculations, this requires highly optimized algorithms and cutting-edge high performance computing (HPC) resources. Progress over the project period is discussed in detail in the following subsections
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing
2016-11-01
These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.
Lattice investigations of the QCD phase diagram
International Nuclear Information System (INIS)
Guenther, Jana
2016-01-01
To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.
Lattice investigations of the QCD phase diagram
Energy Technology Data Exchange (ETDEWEB)
Guenther, Jana
2016-12-15
To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.
Spin-2 NΩ dibaryon from lattice QCD
International Nuclear Information System (INIS)
Etminan, Faisal; Nemura, Hidekatsu; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Sasaki, Kenji
2014-01-01
We investigate properties of the N(nucleon)–Ω(Omega) interaction in lattice QCD to seek for possible dibaryon states in the strangeness −3 channel. We calculate the NΩ potential through the equal-time Nambu–Bethe–Salpeter wave function in 2+1 flavor lattice QCD with the renormalization group improved Iwasaki gauge action and the nonperturbatively O(a) improved Wilson quark action at the lattice spacing a≃0.12 fm on a (1.9 fm) 3 × 3.8 fm lattice. The ud and s quark masses in our study correspond to m π =875(1) MeV and m K =916(1) MeV. At these parameter values, the central potential in the S-wave with the spin 2 shows attractions at all distances. By solving the Schrödinger equation with this potential, we find one bound state whose binding energy is 18.9(5.0)( +12.1 −1.8 ) MeV, where the first error is the statistical one, while the second represents the systematic error
Spin-2 NΩ dibaryon from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Etminan, Faisal [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Department of Physics, Faculty of Sciences, University of Birjand, Birjand 97175-615 (Iran, Islamic Republic of); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Nemura, Hidekatsu [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Aoki, Sinya [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Doi, Takumi [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Hatsuda, Tetsuo [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Kavli IPMU (WPI), The University of Tokyo, Chiba 277-8583 (Japan); Ikeda, Yoichi [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Inoue, Takashi [Nihon University, College of Bioresource Sciences, Kanagawa 252-0880 (Japan); Ishii, Noriyoshi [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Murano, Keiko [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Sasaki, Kenji [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan)
2014-08-15
We investigate properties of the N(nucleon)–Ω(Omega) interaction in lattice QCD to seek for possible dibaryon states in the strangeness −3 channel. We calculate the NΩ potential through the equal-time Nambu–Bethe–Salpeter wave function in 2+1 flavor lattice QCD with the renormalization group improved Iwasaki gauge action and the nonperturbatively O(a) improved Wilson quark action at the lattice spacing a≃0.12 fm on a (1.9 fm){sup 3}× 3.8 fm lattice. The ud and s quark masses in our study correspond to m{sub π}=875(1) MeV and m{sub K}=916(1) MeV. At these parameter values, the central potential in the S-wave with the spin 2 shows attractions at all distances. By solving the Schrödinger equation with this potential, we find one bound state whose binding energy is 18.9(5.0)({sup +12.1}{sub −1.8}) MeV, where the first error is the statistical one, while the second represents the systematic error.
Deconfining chiral transition in QCD on the lattice
International Nuclear Information System (INIS)
Kanaya, Kazuyuki
1995-01-01
The deconfining chiral transition in finite-temperature QCD is studied on the lattice using Wilson quarks. After discussing the nature of chiral limit with Wilson quarks, we first study the case of two degenerate quarks N F =2, and find that the transition is smooth in the chiral limit on both N t =4 and 6 lattices. For N F =3, on the other hand, clear two state signals are observed for m q t =4 lattices. For a more realistic case of N F =2+1, i.e. two degenerate u and d-quarks and a heavier s-quark, we study the cases m s ≅ 150 and 400 MeV with m u = m d ≅ 0: In contrast to a previous result with staggered quarks, clear two state signals are observed for both cases, suggesting a first order QCD phase transition in the real world. (author)
Energy Technology Data Exchange (ETDEWEB)
Sternbeck, A.
2006-07-18
Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator. (orig.)
Strange Baryon Physics in Full Lattice QCD
International Nuclear Information System (INIS)
Huey-Wen Lin
2007-01-01
Strange baryon spectra and form factors are key probes to study excited nuclear matter. The use of lattice QCD allows us to test the strength of the Standard Model by calculating strange baryon quantities from first principles
Lattice QCD at finite density. An introductory review
International Nuclear Information System (INIS)
Muroya, Shin; Nakamura, Atushi; Nonaka, Chiho; Takaishi, Tetsuya
2003-01-01
This is a pedagogical review of the lattice study of finite density QCD. It is intended to provide the minimum necessary content, so that it may be used as an introduction for newcomers to the field and also for those working in nonlattice areas. After a brief introduction in which we discuss the reasons that finite density QCD is an active and important subject, we present the fundamental formulae that are necessary for the treatment given in the following sections. Next, we survey lattice QCD simulational studies of system with small chemical potentials, of which there have been several prominent works reported recently. Then, two-color QCD calculations are discussed, where we are free from the notorious phase problem and have a chance to consider many new features of finite density QCD. Of special note is the result of recent simulations indicating quark pair condensation and the in-medium effect. Tables of SU(3) and SU(2) lattice simulations at finite baryon density are given. In the next section, we survey several related works that may represent a starting point of future development, although some of these works have not attracted much attention yet. This material is described in a pedagogical manner. Starting from a simple 2-d model, we briefly discuss a lattice analysis of the NJL model. We describe a non-perturbative analytic approach, i.e., the strong coupling approximation method and some results. The canonical ensemble approach, instead of the usual canonical ensemble may be another route to reach high density. We examine the density of state method and show that this old idea includes the recently proposed factorization method. An alternative method, the complex Langevin equation, and an interesting model, the finite isospin model, are also discussed. We give brief comments on a partial sum with respect to Z 3 symmetry and the meron-cluster algorithm, which might solve the sign problem partially or completely. In the Appendix, we discuss several
Finite temperature and chemical potential in lattice QCD and its critical point
International Nuclear Information System (INIS)
Fodor, Z.
2002-01-01
We propose a method to study lattice QCD at finite temperature (T) and chemical potential (μ). We compare the method with direct results and with the Glasgow method by using n f =4 QCD at Im(μ)≠0. We locate the critical endpoint (E) of QCD on the Re(μ)-T plane. We use n f =2+1 dynamical staggered quarks with semi-realistic masses on L t =4 lattices. Our results are based on O(10 3 - 10 4 ) configurations. (orig.)
Parton distributions and lattice QCD calculations: A community white paper
Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; Orginos, Kostas; Rojo, Juan; Accardi, Alberto; Alexandrou, Constantia; Bacchetta, Alessandro; Bozzi, Giuseppe; Chen, Jiunn-Wei; Collins, Sara; Cooper-Sarkar, Amanda; Constantinou, Martha; Del Debbio, Luigi; Engelhardt, Michael; Green, Jeremy; Gupta, Rajan; Harland-Lang, Lucian A.; Ishikawa, Tomomi; Kusina, Aleksander; Liu, Keh-Fei; Liuti, Simonetta; Monahan, Christopher; Nadolsky, Pavel; Qiu, Jian-Wei; Schienbein, Ingo; Schierholz, Gerrit; Thorne, Robert S.; Vogelsang, Werner; Wittig, Hartmut; Yuan, C.-P.; Zanotti, James
2018-05-01
In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.
Phenomenology Using Lattice QCD
Gupta, R.
2005-08-01
This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.
Nuclear Physics from Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage
2011-01-01
We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.
Testing the standard model of particle physics using lattice QCD
International Nuclear Information System (INIS)
Water, Ruth S van de
2007-01-01
Recent advances in both computers and algorithms now allow realistic calculations of Quantum Chromodynamics (QCD) interactions using the numerical technique of lattice QCD. The methods used in so-called '2+1 flavor' lattice calculations have been verified both by post-dictions of quantities that were already experimentally well-known and by predictions that occurred before the relevant experimental determinations were sufficiently precise. This suggests that the sources of systematic error in lattice calculations are under control, and that lattice QCD can now be reliably used to calculate those weak matrix elements that cannot be measured experimentally but are necessary to interpret the results of many high-energy physics experiments. These same calculations also allow stringent tests of the Standard Model of particle physics, and may therefore lead to the discovery of new physics in the future
Italian Physical Society A journey with Roberto in lattice QCD
Lüscher, M
2017-01-01
Lattice field theory and lattice QCD, in particular, are areas of research in which Roberto was strongly interested practically since the beginning of his scientific career. He contributed to the development of lattice QCD through his ideas and publications, but also through his engagement in the APE project and in many other ways as well. Some of the work we did together is recalled in this talk and put in the context of the situation in the field at the time.
Transverse momentum distributions inside the nucleon from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Musch, Bernhard Ulrich
2009-05-29
Nucleons, i.e., protons and neutrons, are composed of quarks and gluons, whose interactions are described by the theory of quantum chromodynamics (QCD), part of the standard model of particle physics. This work applies lattice QCD to compute quark momentum distributions in the nucleon. The calculations make use of lattice data generated on supercomputers that has already been successfully employed in lattice studies of spatial quark distributions (''nucleon tomography''). In order to be able to analyze transverse momentum dependent parton distribution functions, this thesis explores a novel approach based on non-local operators. One interesting observation is that the transverse momentum dependent density of polarized quarks in a polarized nucleon is visibly deformed. A more elaborate operator geometry is required to enable a quantitative comparison to high energy scattering experiments. First steps in this direction are encouraging. (orig.)
Lattice simulations of QCD-like theories at finite baryon density
Energy Technology Data Exchange (ETDEWEB)
Scior, Philipp Friedrich
2016-07-13
The exploration of the phase diagram of quantum chromodynamics (QCD) is of great importance to describe e.g. the properties of neutron stars or heavy-ion collisions. Due to the sign problem of lattice QCD at finite chemical potential we need effective theories to study QCD at finite density. Here, we use a three-dimensional Polyakov-loop theory to study the phase diagrams of QCD-like theories. In particular, we investigate the heavy quark limit of the QCD-like theories where the effective theory can be derived from the full theory by a combined strong coupling and hopping expansion. This expansion can be systematically improved order by order. Since there is no sign problem for the QCD-like theories we consider, we can compare our results to data from lattice calculations of the full theories to make qualitative and quantitative statements of the effective theory's validity. We start by deriving the effective theory up to next-to-next-to leading-order, in particular for two-color and G{sub 2}-QCD where replace the three colors in QCD with only two colors or respectively replace the gauge group SU(3) of QCD with G{sub 2}. We will then apply the effective theory at finite temperature mainly to test the theory and the implementation but also to make some predictions for the deconfinement phase transition in G{sub 2} Yang-Mills theory. Finally, we turn our attention to the cold and dense regime of the phase diagram where we observe a sharp increase of the baryon density with the quark chemical potential μ, when μ reaches half the diquark mass. At vanishing temperature this is expected to happen in a quantum phase transition with Bose-Einstein-condensation of diquarks. In contrast to the liquid-gas transition in QCD, the phase transition to the Bose-Einstein condensate is continuous. We find evidence that the effective theories for heavy quarks are able to describe the qualitative difference between first and second order phase transitions. For even higher μ we
Lattice simulations of QCD-like theories at finite baryon density
International Nuclear Information System (INIS)
Scior, Philipp Friedrich
2016-01-01
The exploration of the phase diagram of quantum chromodynamics (QCD) is of great importance to describe e.g. the properties of neutron stars or heavy-ion collisions. Due to the sign problem of lattice QCD at finite chemical potential we need effective theories to study QCD at finite density. Here, we use a three-dimensional Polyakov-loop theory to study the phase diagrams of QCD-like theories. In particular, we investigate the heavy quark limit of the QCD-like theories where the effective theory can be derived from the full theory by a combined strong coupling and hopping expansion. This expansion can be systematically improved order by order. Since there is no sign problem for the QCD-like theories we consider, we can compare our results to data from lattice calculations of the full theories to make qualitative and quantitative statements of the effective theory's validity. We start by deriving the effective theory up to next-to-next-to leading-order, in particular for two-color and G_2-QCD where replace the three colors in QCD with only two colors or respectively replace the gauge group SU(3) of QCD with G_2. We will then apply the effective theory at finite temperature mainly to test the theory and the implementation but also to make some predictions for the deconfinement phase transition in G_2 Yang-Mills theory. Finally, we turn our attention to the cold and dense regime of the phase diagram where we observe a sharp increase of the baryon density with the quark chemical potential μ, when μ reaches half the diquark mass. At vanishing temperature this is expected to happen in a quantum phase transition with Bose-Einstein-condensation of diquarks. In contrast to the liquid-gas transition in QCD, the phase transition to the Bose-Einstein condensate is continuous. We find evidence that the effective theories for heavy quarks are able to describe the qualitative difference between first and second order phase transitions. For even higher μ we find the rise of the
Bottomonium above Deconfinement in Lattice Nonrelativistic QCD
International Nuclear Information System (INIS)
Aarts, G.; Kim, S.; Lombardo, M. P.; Oktay, M. B.; Ryan, S. M.; Sinclair, D. K.; Skullerud, J.-I.
2011-01-01
We study the temperature dependence of bottomonium for temperatures in the range 0.4T c c , using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for N f =2 light flavors on a highly anisotropic lattice. We find that the Υ is insensitive to the temperature in this range, while the χ b propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly free dynamics at T≅2T c .
Properties of the quark gluon plasma from lattice QCD
International Nuclear Information System (INIS)
Mages, Simon Wolfgang
2015-01-01
Quantum Chromodynamics (QCD) is the theory of the strong interaction, the theory of the interaction between the constituents of composite elementary particles (hadrons). In the low energy regime of the theory, standard methods of theoretical physics like perturbative approaches break down due to a large value of the coupling constant. However, this is the region of most interest, where the degrees of freedom of QCD, the color charges, form color-neutral composite elementary particles, like protons and neutrons. Also the transition to more energetic states of matter like the quark gluon plasma (QGP), is difficult to investigate with perturbative approaches. A QGP is a state of strongly interacting matter, which existed shortly after the Big Bang and can be created with heavy ion collisions for example at the LHC at CERN. In a QGP the color charges of QCD are deconfined. This thesis explores ways how to use the non-perturbative approach of lattice QCD to determine properties of the QGP. It focuses mostly on observables which are derived from the energy momentum tensor, like two point correlation functions. In principle these contain information on low energy properties of the QGP like the shear and bulk viscosity and other transport coefficients. The thesis describes the lattice QCD simulations which are necessary to measure the correlation functions and proposes new methods to extract these low energy properties. The thesis also tries to make contact to another non-perturbative approach which is Improved Holographic QCD. The aim of this approach is to use the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence to make statements about QCD with calculations of a five dimensional theory of gravity. This thesis contributes to that work by constraining the parameters of the model action by comparing the predictions with those of measurements with lattice QCD.
Constructing a neutron star from the lattice in G{sub 2}-QCD
Energy Technology Data Exchange (ETDEWEB)
Hajizadeh, Ouraman; Maas, Axel [University of Graz, Institute of Physics, NAWI Graz (Austria)
2017-10-15
The inner structure of neutron stars is still an open question. One obstacle is the infamous sign problem of lattice QCD, which bars access to the high-density equation of state. A possibility to make progress and understand the qualitative impact of gauge interactions on the neutron star structure is to study a modified version of QCD without the sign problem. In the modification studied here the gauge group of QCD is replaced by the exceptional Lie group G{sub 2}, which keeps neutrons in the spectrum. Using an equation of state from lattice calculations only we determine the mass-radius-relation for a neutron star using the Tolman-Oppenheimer-Volkoff equation. This allows us to understand the challenges and approximations currently necessary to use lattice data for this purpose. We discuss in detail the particular uncertainties and systematic problems of this approach. (orig.)
Hadron physics from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Andreas [Regensburg Univ. (Germany). Inst. for Theoretical Physics
2016-11-01
Particle physics experiments at modern high luminosity particle accelerators achieve orders of magnitude higher count rates than what was possible ten or twenty years ago. This extremely large statistics allows to draw far reaching conclusions even from minute signals, provided that these signals are well understood by theory. This is, however, ever more difficult to achieve. Presently, technical and scientific progress in general and experimental progress in particle physics in particular, shows typically an exponential growth rate. For example, data acquisition and analysis are, among many other factor, driven by the development of ever more efficient computers and thus by Moore's law. Theory has to keep up with this development by also achieving an exponential increase in precision, which is only possible using powerful computers. This is true for both types of calculations, analytic ones as, e.g., in quantum field perturbation theory, and purely numerical ones as in Lattice QCD. As stated above such calculations are absolutely indispensable to make best use of the extremely costly large particle physics experiments. Thus, it is economically reasonable to invest a certain percentage of the cost of accelerators and experiments in related theory efforts. The basic ideas behind Lattice QCD simulations are the following: Because quarks and gluons can never be observed individually but are always ''confined'' into colorless hadrons, like the proton, all quark-gluon states can be expressed in two different systems of basis states, namely in a quark-gluon basis and the basis of hadron states. The proton, e.g., is an eigenstate of the latter, a specific quark-gluon configuration is part of the former. In the quark-gluon basis a physical hadron, like a proton, is given by an extremely complicated multi-particle wave function containing all effects of quantum fluctuations. This state is so complicated that it is basically impossible to model it
Lattice-QCD based Schwinger-Dyson approach for Chiral phase transition
International Nuclear Information System (INIS)
Iida, Hideaki; Oka, Makoto; Suganuma, Hideo
2005-01-01
Dynamical chiral-symmetry breaking in QCD is studied with the Schwinger-Dyson (SD) formalism based on lattice QCD data, i.e., LQCD-based SD formalism. We extract the SD kernel function K(p 2 ) in an Ansatzindependent manner from the lattice data of the quark propagator in the Landau gauge. As remarkable features, we find infrared vanishing and intermediate enhancement of the SD kernel function K(p 2 ). We apply the LQCD-based SD equation to thermal QCD with the quark chemical potential μ q . We find chiral symmetry restoration at T c ∼100MeV for μ q =0. The real part of the quark mass function decreases as T and μ q . At finite density, there appears the imaginary part of the quark mass function, which would lead to the width broadening of hadrons
Computing for Lattice QCD: new developments from the APE experiment
Energy Technology Data Exchange (ETDEWEB)
Ammendola, R [INFN, Sezione di Roma Tor Vergata, Roma (Italy); Biagioni, A; De Luca, S [INFN, Sezione di Roma, Roma (Italy)
2008-06-15
As the Lattice QCD develops improved techniques to shed light on new physics, it demands increasing computing power. The aim of the current APE (Array Processor Experiment) project is to provide the reference computing platform to the Lattice QCD community for the period 2009-2011. We present the project proposal for a peta flops range super-computing center with high performance and low maintenance costs, to be delivered starting from 2010.
Computing for Lattice QCD: new developments from the APE experiment
International Nuclear Information System (INIS)
Ammendola, R.; Biagioni, A.; De Luca, S.
2008-01-01
As the Lattice QCD develops improved techniques to shed light on new physics, it demands increasing computing power. The aim of the current APE (Array Processor Experiment) project is to provide the reference computing platform to the Lattice QCD community for the period 2009-2011. We present the project proposal for a peta flops range super-computing center with high performance and low maintenance costs, to be delivered starting from 2010.
Lattice QCD Calculation of Nucleon Structure
International Nuclear Information System (INIS)
Liu, Keh-Fei; Draper, Terrence
2016-01-01
It is emphasized in the 2015 NSAC Long Range Plan that 'understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics.' Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, ?NN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the 'quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the D_s meson decay constant f_D__s, the strangeness and charmness, the meson mass decomposition and the strange quark spin from the
Towards the petaflop for Lattice QCD simulations the PetaQCD project
International Nuclear Information System (INIS)
D'Auriac, Jean-Christian Angles; Carbonell, Jaume; Barthou, Denis
2010-01-01
The study and design of a very ambitious petaflop cluster exclusively dedicated to Lattice QCD simulations started in early '08 among a consortium of 7 laboratories (IN2P3, CNRS, INRIA, CEA) and 2 SMEs. This consortium received a grant from the French ANR agency in July '08, and the PetaQCD project kickoff took place in January '09. Building upon several years of fruitful collaborative studies in this area, the aim of this project is to demonstrate that the simulation of a 256 x 128 3 lattice can be achieved through the HMC/ETMC software, using a machine with efficient speed/cost/reliability/power consumption ratios. It is expected that this machine can be built out of a rather limited number of processors (e.g. between 1000 and 4000), although capable of a sustained petaflop CPU performance. The proof-of-concept should be a mock-up cluster built as much as possible with off-the-shelf components, and 2 particularly attractive axis will be mainly investigated, in addition to fast all-purpose multi-core processors: the use of the new brand of IBM-Cell processors (with on-chip accelerators) and the very recent Nvidia GP-GPUs (off-chip co-processors). This cluster will obviously be massively parallel, and heterogeneous. Communication issues between processors, implied by the Physics of the simulation and the lattice partitioning, will certainly be a major key to the project.
Lattice QCD results on soft and hard probes of strongly interacting matter
Kaczmarek, Olaf
2017-11-01
We present recent results from lattice QCD relevant for the study of strongly interacting matter as it is produced in heavy ion collision experiments. The equation of state at non-vanishing density from a Taylor expansion up to 6th order will be discussed for a strangeness neutral system and using the expansion coefficients of the series limits on the critical point are estimated. Chemical freeze-out temperatures from the STAR and ALICE Collaborations will be compared to lines of constant physics calculated from the Taylor expansion of QCD bulk thermodynamic quantities. We show that qualitative features of the √{sNN} dependence of skewness and kurtosis ratios of net proton-number fluctuations measured by the STAR Collaboration can be understood from QCD results for cumulants of conserved baryon-number fluctuations. As an example for recent progress towards the determination of spectral and transport properties of the QGP from lattice QCD, we will present constraints on the thermal photon rate determined from a spectral reconstruction of continuum extrapolated lattice correlation functions in combination with input from most recent perturbative calculations.
Energy Technology Data Exchange (ETDEWEB)
Buechner, O. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Ernst, M. [Deutsches Elektronen-Synchrotron DESY, 22603 Hamburg (Germany); Jansen, K. [John von Neumann-Institut fuer Computing NIC/DESY, 15738 Zeuthen (Germany); Lippert, Th. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Melkumyan, D. [Deutsches Elektronen-Synchrotron DESY, 15738 Zeuthen (Germany); Orth, B. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Pleiter, D. [John von Neumann-Institut fuer Computing NIC/DESY, 15738 Zeuthen (Germany)]. E-mail: dirk.pleiter@desy.de; Stueben, H. [Konrad-Zuse-Institut fuer Informationstechnik ZIB, 14195 Berlin (Germany); Wegner, P. [Deutsches Elektronen-Synchrotron DESY, 15738 Zeuthen (Germany); Wollny, S. [Konrad-Zuse-Institut fuer Informationstechnik ZIB, 14195 Berlin (Germany)
2006-04-01
As the need for computing resources to carry out numerical simulations of Quantum Chromodynamics (QCD) formulated on a lattice has increased significantly, efficient use of the generated data has become a major concern. To improve on this, groups plan to share their configurations on a worldwide level within the International Lattice DataGrid (ILDG). Doing so requires standardized description of the configurations, standards on binary file formats and common middleware interfaces. We describe the requirements and problems, and discuss solutions. Furthermore, an overview is given on the implementation of the LatFor DataGrid [http://www-zeuthen.desy.de/latfor/ldg], a France/German/Italian grid that will be one of the regional grids within the ILDG grid-of-grids concept.
Global QCD Analysis of the Nucleon Tensor Charge with Lattice QCD Constraints
Shows, Harvey, III; Melnitchouk, Wally; Sato, Nobuo
2017-09-01
By studying the parton distribution functions (PDFs) of a nucleon, we probe the partonic scale of nature, exploring what it means to be a nucleon. In this study, we are interested in the transversity PDF-the least studied of the three collinear PDFs. By conducting a global analysis on experimental data from semi-inclusive deep inelastic scattering (SIDIS), as well as single-inclusive e+e- annihilation (SIA), we extract the fit parameters needed to describe the transverse moment dependent (TMD) transversity PDF, as well as the Collins fragmentation function. Once the collinear transversity PDF is obtained by integrating the extracted TMD PDF, we wish to resolve discrepancies between lattice QCD calculations and phenomenological extractions of the tensor charge from data. Here we show our results for the transversity distribution and tensor charge. Using our method of iterative Monte Carlo, we now have a more robust understanding of the transversity PDF. With these results we are able to progress in our understanding of TMD PDFs, as well as testify to the efficacy of current lattice QCD calculations. This work is made possible through support from NSF award 1659177 to Old Dominion University.
Lattice QCD inputs to the CKM unitarity triangle analysis
International Nuclear Information System (INIS)
Laiho, Jack; Lunghi, E.; Van de Water, Ruth S.
2010-01-01
We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner: whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters B-circumflex K , |V cb |, and |V ub |/|V cb |. We find a (2-3)σ tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of |V cb |. If we interpret the tension as a sign of new physics in either neutral kaon or B mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.
QCD propagators and vertices from lattice QCD (in memory of Michael Müller-Preußker
Directory of Open Access Journals (Sweden)
Sternbeck André
2017-01-01
Full Text Available We review lattice calculations of the elementary Greens functions of QCD with a special emphasis on the Landau gauge. These lattice results have been of interest to continuum approaches to QCD over the past 20 years. They are used as reference for Dyson-Schwinger- and functional renormalization group equation calculations as well as for hadronic bound state equations. The lattice provides low-energy data for propagators and three-point vertices in Landau gauge at zero and finite temperature even including dynamical fermions. We summarize Michael Müller-Preußker’s important contributions to this field and put them into the perspective of his other research interests.
Local coherence and deflation of the low quark modes in lattice QCD
International Nuclear Information System (INIS)
Luescher, Martin
2007-01-01
The spontaneous breaking of chiral symmetry in QCD is known to be linked to a non-zero density of eigenvalues of the massless Dirac operator near the origin. Numerical studies of two-flavour QCD now suggest that the low quark modes are locally coherent to a certain extent. As a consequence, the modes can be simultaneously deflated, using local projectors, with a total computational effort proportional to the lattice volume (rather than its square). Deflation has potentially many uses in lattice QCD. The technique is here worked out for the case of quark propagator calculations, where large speed-up factors and a flat scaling behaviour with respect to the quark mass are achieved
Local coherence and deflation of the low quark modes in lattice QCD
Lüscher, Martin
2007-01-01
The spontaneous breaking of chiral symmetry in QCD is known to be linked to a non-zero density of eigenvalues of the massless Dirac operator near the origin. Numerical studies of two-flavour QCD now suggest that the low quark modes are locally coherent to a certain extent. As a consequence, the modes can be simultaneously deflated, using local projectors, with a total computational effort proportional to the lattice volume (rather than its square). Deflation has potentially many uses in lattice QCD. The technique is here worked out for the case of quark propagator calculations, where large speed-up factors and a flat scaling behaviour with respect to the quark mass are achieved.
Nucleon deformation from lattice QCD
International Nuclear Information System (INIS)
Tsapalis, A.
2008-01-01
The issue of nucleon and Delta(1232) deformation is discussed through the evaluation of the N to Delta electromagnetic transition and Delta electromagnetic form factors in Lattice QCD. The momentum dependence of the form factors is studied using 2+1 staggered dynamical flavors at pion masses as low as 350 MeV and compared to results obtained in the Wilson quenched and two-flavor dynamical theory at similar pion masses. The measurement of small non-zero quadrupole amplitudes, in agreement to recent experiments, establishes the existence of deformation in the N and Delta states. (author)
Recent development and perspectives of machines for lattice QCD
International Nuclear Information System (INIS)
Lippert, Th.
2004-01-01
I am going to highlight recent progress in cluster computer technology and to assess status and prospects of cluster computers for lattice QCD with respect to the development of QCDOC and apeNEXT. Taking the LatFor test case, I specify a 512-processor QCD-cluster better than 1$/Mflops
Quark–gluon plasma phenomenology from anisotropic lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Skullerud, Jon-Ivar; Kelly, Aoife [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Aarts, Gert; Allton, Chris; Amato, Alessandro; Evans, P. Wynne M.; Hands, Simon [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Burnier, Yannis [Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne (Switzerland); Giudice, Pietro [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, Tim; Ryan, Sinéad M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kim, Seyong [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, Maria Paola [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Oktay, Mehmet B. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Rothkopf, Alexander [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D–69120 Heidelberg (Germany)
2016-01-22
The FASTSUM collaboration has been carrying out simulations of N{sub f} = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.
Hadronic corrections to electroweak observables from twisted mass lattice QCD
International Nuclear Information System (INIS)
Pientka, Grit
2015-01-01
For several benchmark quantities investigated to detect signs for new physics beyond the standard model of elementary particle physics, lattice QCD currently constitutes the only ab initio approach available at small momentum transfers for the computation of non-perturbative hadronic contributions. Among those observables are the lepton anomalous magnetic moments and the running of the electroweak coupling constants. We compute the leading QCD contribution to the muon anomalous magnetic moment by performing lattice QCD calculations on ensembles incorporating N f =2+1+1 dynamical twisted mass fermions. Considering active up, down, strange, and charm quarks, admits for the first time a direct comparison of the lattice data for the muon anomaly with phenomenological results because both the latter as well as the experimentally obtained values are sensitive to the complete first two generations of quarks at the current level of precision. Recently, it has been noted that improved measurements of the electron and tau anomalous magnetic moments might also provide ways of detecting new physics contributions. Therefore, we also compute their leading QCD contributions, which simultaneously serve as cross-checks of the value obtained for the muon. Additionally, we utilise the obtained data to compute the leading hadronic contribution to the running of the fine structure constant, which enters all perturbative QED calculations. Furthermore, we show that even for the weak mixing angle the leading QCD contribution can be computed from this data. In this way, we identify a new prime observable in the search for new physics whose hadronic contributions can be obtained from lattice QCD. With the results obtained in this thesis, we are able to exclude unsuitable phenomenologically necessary flavour separations and thus directly assist the presently more precise phenomenological determinations of this eminent quantity.
Benchmarking computer platforms for lattice QCD applications
International Nuclear Information System (INIS)
Hasenbusch, M.; Jansen, K.; Pleiter, D.; Stueben, H.; Wegner, P.; Wettig, T.; Wittig, H.
2004-01-01
We define a benchmark suite for lattice QCD and report on benchmark results from several computer platforms. The platforms considered are apeNEXT, CRAY T3E; Hitachi SR8000, IBM p690, PC-Clusters, and QCDOC
Searching for beauty-fully bound tetraquarks using lattice nonrelativistic QCD
Hughes, Ciaran; Eichten, Estia; Davies, Christine T. H.
2018-03-01
Motivated by multiple phenomenological considerations, we perform the first search for the existence of a b ¯b ¯b b tetraquark bound state with a mass below the lowest noninteracting bottomonium-pair threshold using the first-principles lattice nonrelativistic QCD methodology. We use a full S -wave color/spin basis for the b ¯b ¯b b operators in the three 0++, 1+- and 2++ channels. We employ four gluon field ensembles at multiple lattice spacing values ranging from a =0.06 - 0.12 fm , all of which include u , d , s and c quarks in the sea, and one ensemble which has physical light-quark masses. Additionally, we perform novel exploratory work with the objective of highlighting any signal of a near threshold tetraquark, if it existed, by adding an auxiliary potential into the QCD interactions. With our results we find no evidence of a QCD bound tetraquark below the lowest noninteracting thresholds in the channels studied.
Lattice QCD Application Development within the US DOE Exascale Computing Project
Energy Technology Data Exchange (ETDEWEB)
Brower, Richard [Boston U.; Christ, Norman [Columbia U.; DeTar, Carleton [Utah U.; Edwards, Robert [Jefferson Lab; Mackenzie, Paul [Fermilab
2017-10-30
In October, 2016, the US Department of Energy launched the Exascale Computing Project, which aims to deploy exascale computing resources for science and engineering in the early 2020's. The project brings together application teams, software developers, and hardware vendors in order to realize this goal. Lattice QCD is one of the applications. Members of the US lattice gauge theory community with significant collaborators abroad are developing algorithms and software for exascale lattice QCD calculations. We give a short description of the project, our activities, and our plans.
Lattice QCD Application Development within the US DOE Exascale Computing Project
Brower, Richard; Christ, Norman; DeTar, Carleton; Edwards, Robert; Mackenzie, Paul
2018-03-01
In October, 2016, the US Department of Energy launched the Exascale Computing Project, which aims to deploy exascale computing resources for science and engineering in the early 2020's. The project brings together application teams, software developers, and hardware vendors in order to realize this goal. Lattice QCD is one of the applications. Members of the US lattice gauge theory community with significant collaborators abroad are developing algorithms and software for exascale lattice QCD calculations. We give a short description of the project, our activities, and our plans.
Lattice QCD Application Development within the US DOE Exascale Computing Project
Directory of Open Access Journals (Sweden)
Brower Richard
2018-01-01
Full Text Available In October, 2016, the US Department of Energy launched the Exascale Computing Project, which aims to deploy exascale computing resources for science and engineering in the early 2020’s. The project brings together application teams, software developers, and hardware vendors in order to realize this goal. Lattice QCD is one of the applications. Members of the US lattice gauge theory community with significant collaborators abroad are developing algorithms and software for exascale lattice QCD calculations. We give a short description of the project, our activities, and our plans.
Status and prospects for the calculation of hadron structure from lattice QCD
International Nuclear Information System (INIS)
Renner, Dru B.
2010-02-01
Lattice QCD calculations of hadron structure are a valuable complement to many experimental programs as well as an indispensable tool to understand the dynamics of QCD. I present a focused review of a few representative topics chosen to illustrate both the challenges and advances of our community: the momentum fraction, axial charge and charge radius of the nucleon. I will discuss the current status of these calculations and speculate on the prospects for accurate calculations of hadron structure from lattice QCD. (orig.)
Uncertainty quantification in lattice QCD calculations for nuclear physics
Energy Technology Data Exchange (ETDEWEB)
Beane, Silas R. [Univ. of Washington, Seattle, WA (United States); Detmold, William [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Orginos, Kostas [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Savage, Martin J. [Institute for Nuclear Theory, Seattle, WA (United States)
2015-02-05
The numerical technique of Lattice QCD holds the promise of connecting the nuclear forces, nuclei, the spectrum and structure of hadrons, and the properties of matter under extreme conditions with the underlying theory of the strong interactions, quantum chromodynamics. A distinguishing, and thus far unique, feature of this formulation is that all of the associated uncertainties, both statistical and systematic can, in principle, be systematically reduced to any desired precision with sufficient computational and human resources. As a result, we review the sources of uncertainty inherent in Lattice QCD calculations for nuclear physics, and discuss how each is quantified in current efforts.
Benchmarking computer platforms for lattice QCD applications
International Nuclear Information System (INIS)
Hasenbusch, M.; Jansen, K.; Pleiter, D.; Wegner, P.; Wettig, T.
2003-09-01
We define a benchmark suite for lattice QCD and report on benchmark results from several computer platforms. The platforms considered are apeNEXT, CRAY T3E, Hitachi SR8000, IBM p690, PC-Clusters, and QCDOC. (orig.)
Cluster computing for lattice QCD simulations
International Nuclear Information System (INIS)
Coddington, P.D.; Williams, A.G.
2000-01-01
Full text: Simulations of lattice quantum chromodynamics (QCD) require enormous amounts of compute power. In the past, this has usually involved sharing time on large, expensive machines at supercomputing centres. Over the past few years, clusters of networked computers have become very popular as a low-cost alternative to traditional supercomputers. The dramatic improvements in performance (and more importantly, the ratio of price/performance) of commodity PCs, workstations, and networks have made clusters of off-the-shelf computers an attractive option for low-cost, high-performance computing. A major advantage of clusters is that since they can have any number of processors, they can be purchased using any sized budget, allowing research groups to install a cluster for their own dedicated use, and to scale up to more processors if additional funds become available. Clusters are now being built for high-energy physics simulations. Wuppertal has recently installed ALiCE, a cluster of 128 Alpha workstations running Linux, with a peak performance of 158 G flops. The Jefferson Laboratory in the US has a 16 node Alpha cluster and plans to upgrade to a 256 processor machine. In Australia, several large clusters have recently been installed. Swinburne University of Technology has a cluster of 64 Compaq Alpha workstations used for astrophysics simulations. Early this year our DHPC group constructed a cluster of 116 dual Pentium PCs (i.e. 232 processors) connected by a Fast Ethernet network, which is used by chemists at Adelaide University and Flinders University to run computational chemistry codes. The Australian National University has recently installed a similar PC cluster with 192 processors. The Centre for the Subatomic Structure of Matter (CSSM) undertakes large-scale high-energy physics calculations, mainly lattice QCD simulations. The choice of the computer and network hardware for a cluster depends on the particular applications to be run on the machine. Our
Light hadron spectrum from quenched lattice QCD. Results from the CP-PACS
International Nuclear Information System (INIS)
Yoshie, Tomoteru
2001-01-01
Deriving the light hadron spectrum from first principles of QCD has been a fundamental issue in elementary particle physics since the mid-1970s, when QCD was established. With this goal in mind, we have carried out large-scale simulations of lattice QCD on the CP-PACS computer. In this article, we present results for the light hadron spectrum derived in the quenched approximation to lattice QCD. We find that although the global structure of the observed spectrum is reproduced, the quenched spectrum systematically deviates from experiment when examined with an accuracy at better than a 10% level. Results for light quark masses are also reported. Another simulation of full QCD done recently (also on the CP-PACS computer) shows indications that the discrepancy observed in quenched QCD is significantly reduced by the introduction of two flavors of light dynamical quarks. (author)
Extracting the Omega- electric quadrupole moment from lattice QCD data
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, M.T. Pena
2011-03-01
The Omega- has an extremely long lifetime, and is the most stable of the baryons with spin 3/2. Therefore the Omega- magnetic moment is very accurately known. Nevertheless, its electric quadrupole moment was never measured, although estimates exist in different formalisms. In principle, lattice QCD simulations provide at present the most appropriate way to estimate the Omega- form factors, as function of the square of the transferred four-momentum, Q2, since it describes baryon systems at the physical mass for the strange quark. However, lattice QCD form factors, and in particular GE2, are determined at finite Q2 only, and the extraction of the electric quadrupole moment, Q_Omega= GE2(0) e/(2 M_Omega), involves an extrapolation of the numerical lattice results. In this work we reproduce the lattice QCD data with a covariant spectator quark model for Omega- which includes a mixture of S and two D states for the relative quark-diquark motion. Once the model is calibrated, it is used to determine Q_Omega. Our prediction is Q_Omega= (0.96 +/- 0.02)*10^(-2) efm2 [GE2(0)=0.680 +/- 0.012].
Lattice QCD Calculation of Nucleon Structure
Energy Technology Data Exchange (ETDEWEB)
Liu, Keh-Fei [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy; Draper, Terrence [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy
2016-08-30
It is emphasized in the 2015 NSAC Long Range Plan that "understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, πNN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the D_{s} meson decay constant f_{Ds}, the strangeness and charmness, the meson mass
Electromagnetic form factors at large momenta from lattice QCD
International Nuclear Information System (INIS)
Chambers, Alexander J.; Dragos, J.; Michigan State Univ., East Lansing, MI; Horsley, R.
2017-01-01
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavours of degenerate mass quarks corresponding to m_π∼470 MeV. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately 6 GeV"2, with results for G_E/G_M in the proton agreeing well with experimental results.
Phase transitions: the lattice QCD approach
International Nuclear Information System (INIS)
Gavai, R.V.
1986-01-01
Recent results in the field of finite temperature lattice quantum chromodynamics (QCD) are presented with special emphasis on comparison of the different methods used to incorporate the dynamical fermions. Attempts to obtain a nonperturbative estimate of the velocity of sound in both the hadronic and quark-gluon phase are summarized along with the results. 15 refs., 7 figs
Flavor extrapolation in lattice QCD
International Nuclear Information System (INIS)
Duffy, W.C.
1984-01-01
Explicit calculation of the effect of virtual quark-antiquark pairs in lattice QCD has eluded researchers. To include their effect explicitly one must calculate the determinant of the fermion-fermion coupling matrix. Owing to the large number of sites in a continuum limit size lattice, direct evaluation of this term requires an unrealistic amount of computer time. The effect of the virtual pairs can be approximated by ignoring this term and adjusting lattice couplings to reproduce experimental results. This procedure is called the valence approximation since it ignores all but the minimal number of quarks needed to describe hadrons. In this work the effect of the quark-antiquark pairs has been incorporated in a theory with an effective negative number of quark flavors contributing to the closed loops. Various particle masses and decay constants have been calculated for this theory and for one with no virtual pairs. The author attempts to extrapolate results towards positive numbers of quark flavors. The results show approximate agreement with experimental measurements and demonstrate the smoothness of lattice expectations in the number of quark flavors
B-physics from lattice QCD...with a twist
Carrasco, N.; Frezzotti, R.; Gimenez, V.; Herdoiza, G.; Lubicz, V.; Martinelli, G.; Michael, C.; Palao, D.; Rossi, G.C.; Sanfilippo, F.; Shindler, A.; Simula, S.; Tarantino, C.
2012-01-01
We present a precise lattice QCD determination of the b-quark mass, of the B and Bs decay constants and first results for the B-meson bag parameters. For our computation we employ the so-called ratio method and our results benefit from the use of improved interpolating operators for the B-mesons. QCD calculations are performed with Nf = 2 dynamical light-quarks at four values of the lattice spacing and the results are extrapolated to the continuum limit. The preliminary results are mb(mb) = 4.35(12) GeV for the MSbar b-quark mass, fBs = 234(6) MeV and fB = 197(10) MeV for the B-meson decay constants, BBs(mb) = 0.90(5) and BB(mb) = 0.87(5) for the B-meson bag parameters.
Precision Light Flavor Physics from Lattice QCD
Murphy, David
In this thesis we present three distinct contributions to the study of light flavor physics using the techniques of lattice QCD. These results are arranged into four self-contained papers. The first two papers concern global fits of the quark mass, lattice spacing, and finite volume dependence of the pseudoscalar meson masses and decay constants, computed in a series of lattice QCD simulations, to partially quenched SU(2) and SU(3) chiral perturbation theory (chiPT). These fits determine a subset of the low energy constants of chiral perturbation theory -- in some cases with increased precision, and in other cases for the first time -- which, once determined, can be used to compute other observables and amplitudes in chiPT. We also use our formalism to self-consistently probe the behavior of the (asymptotic) chiral expansion as a function of the quark masses by repeating the fits with different subsets of the data. The third paper concerns the first lattice QCD calculation of the semileptonic K0 → pi-l +nul ( Kl3) form factor at vanishing momentum transfer, f+Kpi(0), with physical mass domain wall quarks. The value of this form factor can be combined with a Standard Model analysis of the experimentally measured K0 → pi -l+nu l decay rate to extract a precise value of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vus, and to test unitarity of the CKM matrix. We also discuss lattice calculations of the pion and kaon decay constants, which can be used to extract Vud through an analogous Standard Model analysis of experimental constraints on leptonic pion and kaon decays. The final paper explores the recently proposed exact one flavor algorithm (EOFA). This algorithm has been shown to drastically reduce the memory footprint required to simulate single quark flavors on the lattice relative to the widely used rational hybrid Monte Carlo (RHMC) algorithm, while also offering modest O(20%) speed-ups. We independently derive the exact one flavor action, explore its
The heavy quark-antiquark potential from lattice and perturbative QCD
Laschka, Alexander; Kaiser, Norbert; Weise, Wolfram
2009-01-01
The heavy quark-antiquark potential in perturbative QCD is subject to ambiguities. We show how to derive a well-defined and stable short-distance potential that can be matched to results from lattice QCD simulations at intermediate distances. The static potential as well as the order 1/m potential are discussed.
Lattice QCD on new chips: a community summary
Directory of Open Access Journals (Sweden)
Rago Antonio
2018-01-01
Full Text Available I review the most recent evolutions of the QCD codes on new architectures, with a focus on the performances obtained by the different coding strategies as presented during the Lattice2017 conference.
Nucleon generalized parton distributions from full lattice QCD
International Nuclear Information System (INIS)
Haegler, P.; Schroers, W.; Bratt, J.; Negele, J.W.; Pochinsky, A.V.
2007-07-01
We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N f =2+1 lattice QCD using domain wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5 fm) 3 . (orig.)
Nucleon electromagnetic form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Koutsou, G.; Negele, J. W.; Tsapalis, A.
2006-01-01
We evaluate the isovector nucleon electromagnetic form factors in quenched and unquenched QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at β=6.0 enabling us to reach low momentum transfers and a lowest pion mass of about 400 MeV. In the unquenched theory we use two degenerate flavors of dynamical Wilson fermions on a lattice of spatial size 1.9 fm at β=5.6 and lowest pion mass of about 380 MeV enabling comparison with the results obtained in the quenched theory. that unquenching effects are small for the pion masses considered in this work. We compare our lattice results to the isovector part of the experimentally measured form factors
Electromagnetic form factors at large momenta from lattice QCD
Chambers, A. J.; Dragos, J.; Horsley, R.; Nakamura, Y.; Perlt, H.; Pleiter, D.; Rakow, P. E. L.; Schierholz, G.; Schiller, A.; Somfleth, K.; Stüben, H.; Young, R. D.; Zanotti, J. M.; Qcdsf/Ukqcd/Cssm Collaborations
2017-12-01
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here, we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavors of degenerate mass quarks corresponding to mπ≈470 MeV . We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately 6 GeV2 , with results for the ratio of the electric and magnetic form factors of the proton at our simulated quark mass agreeing well with experimental results.
Critical slowing down and error analysis in lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Virotta, Francesco
2012-02-21
In this work we investigate the critical slowing down of lattice QCD simulations. We perform a preliminary study in the quenched approximation where we find that our estimate of the exponential auto-correlation time scales as {tau}{sub exp}(a){proportional_to}a{sup -5}, where a is the lattice spacing. In unquenched simulations with O(a) improved Wilson fermions we do not obtain a scaling law but find results compatible with the behavior that we find in the pure gauge theory. The discussion is supported by a large set of ensembles both in pure gauge and in the theory with two degenerate sea quarks. We have moreover investigated the effect of slow algorithmic modes in the error analysis of the expectation value of typical lattice QCD observables (hadronic matrix elements and masses). In the context of simulations affected by slow modes we propose and test a method to obtain reliable estimates of statistical errors. The method is supposed to help in the typical algorithmic setup of lattice QCD, namely when the total statistics collected is of O(10){tau}{sub exp}. This is the typical case when simulating close to the continuum limit where the computational costs for producing two independent data points can be extremely large. We finally discuss the scale setting in N{sub f}=2 simulations using the Kaon decay constant f{sub K} as physical input. The method is explained together with a thorough discussion of the error analysis employed. A description of the publicly available code used for the error analysis is included.
Critical slowing down and error analysis in lattice QCD simulations
International Nuclear Information System (INIS)
Virotta, Francesco
2012-01-01
In this work we investigate the critical slowing down of lattice QCD simulations. We perform a preliminary study in the quenched approximation where we find that our estimate of the exponential auto-correlation time scales as τ exp (a)∝a -5 , where a is the lattice spacing. In unquenched simulations with O(a) improved Wilson fermions we do not obtain a scaling law but find results compatible with the behavior that we find in the pure gauge theory. The discussion is supported by a large set of ensembles both in pure gauge and in the theory with two degenerate sea quarks. We have moreover investigated the effect of slow algorithmic modes in the error analysis of the expectation value of typical lattice QCD observables (hadronic matrix elements and masses). In the context of simulations affected by slow modes we propose and test a method to obtain reliable estimates of statistical errors. The method is supposed to help in the typical algorithmic setup of lattice QCD, namely when the total statistics collected is of O(10)τ exp . This is the typical case when simulating close to the continuum limit where the computational costs for producing two independent data points can be extremely large. We finally discuss the scale setting in N f =2 simulations using the Kaon decay constant f K as physical input. The method is explained together with a thorough discussion of the error analysis employed. A description of the publicly available code used for the error analysis is included.
Lattice QCD for nuclear physics
Meyer, Harvey
2015-01-01
With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun, and many new observables will be calculated at the new computational facilities. The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems, and in particular to nuclear physics. A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spect...
International Nuclear Information System (INIS)
Sommer, Rainer
2014-02-01
The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.
Energy Technology Data Exchange (ETDEWEB)
Sommer, Rainer [DESY, Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2014-02-15
The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.
Lattice QCD - a challenge in large scale computing
International Nuclear Information System (INIS)
Schilling, K.
1987-01-01
The computation of the hadron spectrum within the framework of lattice QCD sets a demanding goal for the application of supercomputers in basic science. It requires both big computer capacities and clever algorithms to fight all the numerical evils that one encounters in the Euclidean space-time-world. The talk will attempt to introduce to the present state of the art of spectrum calculations by lattice simulations. (orig.)
Thermodynamics of lattice QCD with 2 sextet quarks on Nt=8 lattices
International Nuclear Information System (INIS)
Kogut, J. B.; Sinclair, D. K.
2011-01-01
We continue our lattice simulations of QCD with 2 flavors of color-sextet quarks as a model for conformal or walking technicolor. A 2-loop perturbative calculation of the β function which describes the evolution of this theory's running coupling constant predicts that it has a second zero at a finite coupling. This nontrivial zero would be an infrared stable fixed point, in which case the theory with massless quarks would be a conformal field theory. However, if the interaction between quarks and antiquarks becomes strong enough that a chiral condensate forms before this IR fixed point is reached, the theory is QCD-like with spontaneously broken chiral symmetry and confinement. However, the presence of the nearby IR fixed point means that there is a range of couplings for which the running coupling evolves very slowly, i.e. it ''walks.'' We are simulating the lattice version of this theory with staggered quarks at finite temperature, studying the changes in couplings at the deconfinement and chiral-symmetry restoring transitions as the temporal extent (N t ) of the lattice, measured in lattice units, is increased. Our earlier results on lattices with N t =4, 6 show both transitions move to weaker couplings as N t increases consistent with walking behavior. In this paper we extend these calculations to N t =8. Although both transitions again move to weaker couplings, the change in the coupling at the chiral transition from N t =6 to N t =8 is appreciably smaller than that from N t =4 to N t =6. This indicates that at N t =4, 6 we are seeing strong-coupling effects and that we will need results from N t >8 to determine if the chiral-transition coupling approaches zero as N t →∞, as needed for the theory to walk.
Deflation acceleration of lattice QCD simulations
International Nuclear Information System (INIS)
Luescher, Martin
2007-01-01
Close to the chiral limit, many calculations in numerical lattice QCD can potentially be accelerated using low-mode deflation techniques. In this paper it is shown that the recently introduced domain-decomposed deflation subspaces can be propagated along the field trajectories generated by the Hybrid Monte Carlo (HMC) algorithm with a modest effort. The quark forces that drive the simulation may then be computed using a deflation-accelerated solver for the lattice Dirac equation. As a consequence, the computer time required for the simulations is significantly reduced and an improved scaling behaviour of the simulation algorithm with respect to the quark mass is achieved
Deflation acceleration of lattice QCD simulations
Lüscher, Martin
2007-01-01
Close to the chiral limit, many calculations in numerical lattice QCD can potentially be accelerated using low-mode deflation techniques. In this paper it is shown that the recently introduced domain-decomposed deflation subspaces can be propagated along the field trajectories generated by the Hybrid Monte Carlo (HMC) algorithm with a modest effort. The quark forces that drive the simulation may then be computed using a deflation-accelerated solver for the lattice Dirac equation. As a consequence, the computer time required for the simulations is significantly reduced and an improved scaling behaviour of the simulation algorithm with respect to the quark mass is achieved.
Better than $1/Mflops substained: a scalable PC-based parallel computer for lattice QCD
International Nuclear Information System (INIS)
Fodor, Z.; Papp, G.
2002-02-01
We study the feasibility of a PC-based parallel computer for medium to large scale lattice QCD simulations. Our cluster built at the Eoetvoes Univ., Inst. Theor. Phys. consists of 137 Intel P4-1.7 GHz nodes with 512 MB RDRAM. The 32-bit, single precision sustained performance for dynamical QCD without communication is 1510 Mflops/node with Wilson and 970 Mflops/node with staggered fermions. This gives a total performance of 208 Gflops for Wilson and 133 Gflops for staggered QCD, respectively (for 64-bit applications the performance is approximately halved). The novel feature of our system is its communication architecture. In order to have a scalable, cost-effective machine we use Gigabit Ethernet cards for nearest-neighbor communications in a two-dimensional mesh. This type of communication is cost effective (only 30% of the hardware costs is spent on the communication). According to our benchmark measurements this type of communication results in around 40% communication time fraction for lattices upto 48 3 . 96 in full QCD simulations. The price/sustained-perfomance ratio for full QCD is better than $1/Mflops for Wilson (and around $1.5/Mflops for staggered) quarks for practically any lattice size, which can fit in our parallel computer. (orig.)
A consumer`s guide to lattice QCD results
Energy Technology Data Exchange (ETDEWEB)
DeGrand, T. [Univ. of Colorado, Boulder, CO (United States)
1994-12-01
The author presents an overview of recent lattice QCD results on hadron spectroscopy and matrix elements. Case studies include light quark spectroscopy, the determination of {alpha}{sub s} from heavy quark spectroscopy, the D-meson decay constant, a calculation of the Isgur-Wise function, and some examples of the (lack of) effect of sea quarks on matrix elements. The review is intended for the nonexpert.
Radiative Transitions in Charmonium from Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Jozef Dudek; Robert Edwards; David Richards
2006-01-17
Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the {eta}{sub c}, J/{psi} and {chi}{sub c0}. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched approximation. With an anisotropy {xi} = 3 at a{sub s} {approx} 0.1 fm we find a reasonable gross spectrum and a hyperfine splitting {approx}90 MeV, which compares favorably with other improved actions. In general, after extrapolation of lattice data at non-zero Q{sup 2} to the photopoint, our results agree within errors with all well measured experimental values. Furthermore, results are compared with the expectations of simple quark models where we find that many features are in agreement; beyond this we propose the possibility of constraining such models using our extracted values of physically unobservable quantities such as the J/{psi} quadrupole moment. We conclude that our methods are successful and propose to apply them to the problem of radiative transitions involving hybrid mesons, with the eventual goal of predicting hybrid meson photoproduction rates at the GlueX experiment.
The gluon structure of hadrons and nuclei from lattice QCD
Shanahan, Phiala
2018-03-01
I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon's momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.
Practical Implementation of Lattice QCD Simulation on Intel Xeon Phi Knights Landing
Kanamori, Issaku; Matsufuru, Hideo
2017-01-01
We investigate implementation of lattice Quantum Chromodynamics (QCD) code on the Intel Xeon Phi Knights Landing (KNL). The most time consuming part of the numerical simulations of lattice QCD is a solver of linear equation for a large sparse matrix that represents the strong interaction among quarks. To establish widely applicable prescriptions, we examine rather general methods for the SIMD architecture of KNL, such as using intrinsics and manual prefetching, to the matrix multiplication an...
Meson masses and decay constants from unquenched lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); McNeile, C. [Glasgow Univ. (United Kingdom). Dept. of Physics and Astronomy; Michael, C. [Liverpool Univ. (United Kingdom). Theoretical Physics Div., Dept. of Mathematical Sciences; Urbach, C. [Humboldt Univ. Berlin (Germany). Inst. fuer Physik
2009-06-15
We report results for the masses of the flavour non-singlet light 0{sup ++}, 1{sup --}, and 1{sup +-} mesons from unquenched lattice QCD at two lattice spacings. The twisted mass formalism was used with two flavours of sea quarks. For the 0{sup ++} and 1{sup +-} mesons we look for the effect of decays on the mass dependence. For the light vector mesons we study the chiral extrapolations of the mass. We report results for the leptonic and transverse decay constants of the meson. We test the mass dependence of the KRSF relations. (orig.)
Meson masses and decay constants from unquenched lattice QCD
International Nuclear Information System (INIS)
Jansen, K.; McNeile, C.; Michael, C.; Urbach, C.
2009-06-01
We report results for the masses of the flavour non-singlet light 0 ++ , 1 -- , and 1 +- mesons from unquenched lattice QCD at two lattice spacings. The twisted mass formalism was used with two flavours of sea quarks. For the 0 ++ and 1 +- mesons we look for the effect of decays on the mass dependence. For the light vector mesons we study the chiral extrapolations of the mass. We report results for the leptonic and transverse decay constants of the meson. We test the mass dependence of the KRSF relations. (orig.)
Relevant energy scale of color confinement from lattice QCD
International Nuclear Information System (INIS)
Yamamoto, Arata; Suganuma, Hideo
2009-01-01
We propose a new lattice framework to extract the relevant gluonic energy scale of QCD phenomena which is based on a 'cut' on link variables in momentum space. This framework is expected to be broadly applicable to all lattice QCD calculations. Using this framework, we quantitatively determine the relevant energy scale of color confinement, through the analyses of the quark-antiquark potential and meson masses. The relevant energy scale of color confinement is found to be below 1.5 GeV in the Landau gauge. In fact, the string tension is almost unchanged even after cutting off the high-momentum gluon component above 1.5 GeV. When the relevant low-energy region is cut, the quark-antiquark potential is approximately reduced to a Coulomb-like potential, and each meson becomes a quasifree quark pair. As an analytical model calculation, we also investigate the dependence of the Richardson potential on the cut, and find the consistent behavior with the lattice result.
Axion cosmology, lattice QCD and the dilute instanton gas
International Nuclear Information System (INIS)
Borsanyi, S.; Fodor, Z.; Mages, S.W.; Nogradi, D.; Szabo, K.K.
2015-08-01
Axions are one of the most attractive dark matter candidates. The evolution of their number density in the early universe can be determined by calculating the topological susceptibility χ(T) of QCD as a function of the temperature. Lattice QCD provides an ab initio technique to carry out such a calculation. A full result needs two ingredients: physical quark masses and a controlled continuum extrapolation from non-vanishing to zero lattice spacings. We determine χ(T) in the quenched framework (infinitely large quark masses) and extrapolate its values to the continuum limit. The results are compared with the prediction of the dilute instanton gas approximation (DIGA). A nice agreement is found for the temperature dependence, whereas the overall normalization of the DIGA result still differs from the non-perturbative continuum extrapolated lattice results by a factor of order ten. We discuss the consequences of our findings for the prediction of the amount of axion dark matter.
Statistical Angles on the Lattice QCD Signal-to-Noise Problem
Wagman, Michael L.
The theory of quantum chromodynamics (QCD) encodes the strong interactions that bind quarks and gluons into nucleons and that bind nucleons into nuclei. Predictive control of QCD would allow nuclear structure and reactions as well as properties of supernovae and neutron stars to be theoretically studied from first principles. Lattice QCD (LQCD) can represent generic QCD predictions in terms of well-defined path integrals, but the sign and signal-to-noise problems have obstructed LQCD calculations of large nuclei and nuclear matter in practice. This thesis presents a statistical study of LQCD correlation functions, with a particular focus on characterizing the structure of the noise associated with quantum fluctuations. The signal-to-noise problem in baryon correlation functions is demonstrated to arise from a sign problem associated with Monte Carlo sampling of complex correlation functions. Properties of circular statistics are used to understand the emergence of a large time noise region where standard energy measurements are unreliable. Power-law tails associated with stable distributions and Levy flights are found to play a central role in the time evolution of baryon correlation functions. Building on these observations, a new statistical analysis technique called phase reweighting is introduced that allow energy levels to be extracted from large-time correlation functions with time-independent signal-to-noise ratios. Phase reweighting effectively includes dynamical refinement of source magnitudes but introduces a bias associated with the phase. This bias can be removed by performing an extrapolation, but at the expense of re-introducing a signal-to-noise problem. Lattice QCD calculations of the ρ+ and nucleon masses and of the ΞΞ(1S0) binding energy show consistency between standard results obtained using smaller-time correlation functions and phase-reweighted results using large-time correlation functions inaccessible to standard statistical analysis
Perturbative and nonperturbative renormalization in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [University of Edinburgh (United Kingdom). School of Physics and Astronomy; Perlt, H. [Leipzig Univ. (DE). Institut fuer Theoretische Physik] (and others)
2010-03-15
We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular with recent two-loop calculations. (orig.)
Axial nucleon form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Constantinou, M.; Guichon, P.; Jansen, K.; Korzec, T.
2011-01-01
We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.
Baryon structure from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.
2009-01-01
We present recent lattice results on the baryon spectrum, nucleon electromagnetic and axial form factors, nucleon to Δ transition form factors as well as the Δ electromagnetic form factors. The masses of the low lying baryons and the nucleon form factors are calculated using two degenerate flavors of twisted mass fermions down to pion mass of about 270 MeV. We compare to the results of other collaborations. The nucleon to Δ transition and Δ form factors are calculated in a hybrid scheme, which uses staggered sea quarks and domain wall valence quarks. The dominant magnetic dipole nucleon to Δ transition form factor is also evaluated using dynamical domain wall fermions. The transverse density distributions of the Δ in the infinite momentum frame are extracted using the form factors determined from lattice QCD. (author)
Construction of the dual Ginzburg-Landau theory from the lattice QCD
International Nuclear Information System (INIS)
Suganuma, H.; Amemiya, K.; Ichie, H.; Koma, Y.
2002-01-01
We roughly review the QCD physics and then introduce recent topics on the confinement physics. In the maximally abelian (MA) gauge, the low-energy QCD is abelianized owing to the effective off-diagonal gluon mass M off ≅ 1.2 GeV induced by the MA gauge fixing. We demonstrate the construction of the dual Ginzburg-Landau (DGL) theory from the low-energy QCD in the MA gauge in terms of the lattice QCD evidences on infrared abelian dominance and infrared monopole condensation. (author)
Lattice QCD calculations on commodity clusters at DESY
International Nuclear Information System (INIS)
Gellrich, A.; Pop, D.; Wegner, P.; Wittig, H.; Hasenbusch, M.; Jansen, K.
2003-06-01
Lattice Gauge Theory is an integral part of particle physics that requires high performance computing in the multi-Tflops regime. These requirements are motivated by the rich research program and the physics milestones to be reached by the lattice community. Over the last years the enormous gains in processor performance, memory bandwidth, and external I/O bandwidth for parallel applications have made commodity clusters exploiting PCs or workstations also suitable for large Lattice Gauge Theory applications. For more than one year two clusters have been operated at the two DESY sites in Hamburg and Zeuthen, consisting of 32 resp. 16 dual-CPU PCs, equipped with Intel Pentium 4 Xeon processors. Interconnection of the nodes is done by way of Myrinet. Linux was chosen as the operating system. In the course of the projects benchmark programs for architectural studies were developed. The performance of the Wilson-Dirac Operator (also in an even-odd preconditioned version) as the inner loop of the Lattice QCD (LQCD) algorithms plays the most important role in classifying the hardware basis to be used. Using the SIMD streaming extensions (SSE/SSE2) on Intel's Pentium 4 Xeon CPUs give promising results for both the single CPU and the parallel version. The parallel performance, in addition to the CPU power and the memory throughput, is nevertheless strongly influenced by the behavior of hardware components like the PC chip-set and the communication interfaces. The paper starts by giving a short explanation about the physics background and the motivation for using PC clusters for Lattice QCD. Subsequently, the concept, implementation, and operating experiences of the two clusters are discussed. Finally, the paper presents benchmark results and discusses comparisons to systems with different hardware components including Myrinet-, GigaBit-Ethernet-, and Infiniband-based interconnects. (orig.)
Nucleon axial coupling from Lattice QCD
Cheng Chang, Chia; Nicholson, Amy; Rinaldi, Enrico; Berkowitz, Evan; Garron, Nicolas; Brantley, David; Monge-Camacho, Henry; Monahan, Chris; Bouchard, Chris; Clark, M. A.; Joó, Bálint; Kurth, Thorsten; Orginos, Kostas; Vranas, Pavlos; Walker-Loud, André
2018-03-01
We present state-of-the-art results from a lattice QCD calculation of the nucleon axial coupling, gA, using Möbius Domain-Wall fermions solved on the dynamical Nf = 2 + 1 + 1 HISQ ensembles after they are smeared using the gradient-flow algorithm. Relevant three-point correlation functions are calculated using a method inspired by the Feynman-Hellmann theorem, and demonstrate significant improvement in signal for fixed stochastic samples. The calculation is performed at five pion masses of mπ {400, 350, 310, 220, 130} MeV, three lattice spacings of a {0.15, 0.12, 0.09} fm, and we do a dedicated volume study with mπL {3.22, 4.29, 5.36}. Control over all relevant sources of systematic uncertainty are demonstrated and quantified. We achieve a preliminary value of gA = 1.285(17), with a relative uncertainty of 1.33%.
Supporting the search for the CEP location with nonlocal PNJL models constrained by lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Contrera, Gustavo A. [IFLP, UNLP, CONICET, Facultad de Ciencias Exactas, La Plata (Argentina); Gravitation, Astrophysics and Cosmology Group, FCAyG, UNLP, La Plata (Argentina); CONICET, Buenos Aires (Argentina); Grunfeld, A.G. [CONICET, Buenos Aires (Argentina); Comision Nacional de Energia Atomica, Departamento de Fisica, Buenos Aires (Argentina); Blaschke, David [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland); Joint Institute for Nuclear Research, Moscow Region (Russian Federation); National Research Nuclear University (MEPhI), Moscow (Russian Federation)
2016-08-15
We investigate the possible location of the critical endpoint in the QCD phase diagram based on nonlocal covariant PNJL models including a vector interaction channel. The form factors of the covariant interaction are constrained by lattice QCD data for the quark propagator. The comparison of our results for the pressure including the pion contribution and the scaled pressure shift Δ P/T {sup 4} vs. T/T{sub c} with lattice QCD results shows a better agreement when Lorentzian form factors for the nonlocal interactions and the wave function renormalization are considered. The strength of the vector coupling is used as a free parameter which influences results at finite baryochemical potential. It is used to adjust the slope of the pseudocritical temperature of the chiral phase transition at low baryochemical potential and the scaled pressure shift accessible in lattice QCD simulations. Our study, albeit presently performed at the mean-field level, supports the very existence of a critical point and favors its location within a region that is accessible in experiments at the NICA accelerator complex. (orig.)
The gluon structure of hadrons and nuclei from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Shanahan, Phiala A. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2018-04-01
I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon's momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.
Effective Chiral Lagrangians and Lattice QCD
Heitger, J; Wittig, H; Heitger, Jochen; Sommer, Rainer; Wittig, Hartmut
2000-01-01
We propose a general method to obtain accurate estimates for some of the "low-energy constants" in the one-loop effective chiral Lagrangian by means of simulating lattice QCD. In particular, the method is sensitive to those constants whose values are required to test the hypothesis of a massless up-quark. Initial tests performed in the quenched approximation confirm that good statistical precision can be achieved. As a byproduct we obtain an accurate estimate for the ratio of pseudoscalar decay constants, F_K/F_pi, in the quenched approximation, which lies 10% below the experimental result. The quantities that serve to extract the low-energy constants also allow a test of the scaling behaviour of different discretizations of QCD and a search for the effects of dynamical quarks.
A lattice QCD calculation of the transverse decay constant of the b1(1235) meson
International Nuclear Information System (INIS)
Jansen, K.; McNeile, C.; Michael, C.; Urbach, C.
2009-10-01
We review various B meson decays that require knowledge of the transverse decay constant of the b 1 (1235) meson. We report on an exploratory lattice QCD calculation of the transverse decay constant of the b 1 meson. The lattice QCD calculations used unquenched gauge configurations, at two lattice spacings, generated with two flavours of sea quarks. The twisted mass formalism is used. (orig.)
Exotic meson decay widths using lattice QCD
International Nuclear Information System (INIS)
Cook, M. S.; Fiebig, H. R.
2006-01-01
A decay width calculation for a hybrid exotic meson h, with J PC =1 -+ , is presented for the channel h→πa 1 . This quenched lattice QCD simulation employs Luescher's finite box method. Operators coupling to the h and πa 1 states are used at various levels of smearing and fuzzing, and at four quark masses. Eigenvalues of the corresponding correlation matrices yield energy spectra that determine scattering phase shifts for a discrete set of relative πa 1 momenta. Although the phase shift data is sparse, fits to a Breit-Wigner model are attempted, resulting in a decay width of about 60 MeV when averaged over two lattice sizes having a lattice spacing of 0.07 fm
Development of an object oriented lattice QCD code ''Bridge++''
International Nuclear Information System (INIS)
Ueda, S; Aoki, S; Aoyama, T; Kanaya, K; Taniguchi, Y; Matsufuru, H; Motoki, S; Namekawa, Y; Nemura, H; Ukita, N
2014-01-01
We are developing a new lattice QCD code set ''Bridge++'' aiming at extensible, readable, and portable workbench for QCD simulations, while keeping a high performance at the same time. Bridge++ covers conventional lattice actions and numerical algorithms. The code set is constructed in C++ with an object oriented programming. In this paper we describe fundamental ingredients of the code and the current status of development
Static-light meson masses from twisted mass lattice QCD
International Nuclear Information System (INIS)
Jansen, Karl; Michael, Chris; Shindler, Andrea; Wagner, Marc
2008-08-01
We compute the static-light meson spectrum using two-flavor Wilson twisted mass lattice QCD. We have considered five different values for the light quark mass corresponding to 300 MeV PS S mesons. (orig.)
Hyperon-Nulceon Scattering from Fully-Dynamical Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Silas Beane; Paulo Bedaque; Thomas Luu; Konstantinos Orginos; Elizabetta Pallante; Assumpta Parreno; Martin Savage
2007-10-01
We present results of the first fully-dynamical lattice QCD determination of hyperon-nucleon scattering. One s-wave phase shift was determined for n{Lambda} scattering in both spin-channels at pion masses of 350, 490, and 590 MeV, and for n{Sigma}^- scattering in both spin channels at pion masses of 490, and 590 MeV. The calculations were performed with domain-wall valence quarks on dynamical, staggered gauge configurations with a lattice spacing of b ~0.125 fm.
Aspects of Chiral Symmetry Breaking in Lattice QCD
Horkel, Derek P.
In this thesis we describe two studies concerting lattice quantum chromodynamics (LQCD): first, an analysis of the phase structure of Wilson and twisted-mass fermions with isospin breaking effects, second a computational study measuring non-perturbative Greens functions. We open with a brief overview of the formalism of QCD and LQCD, focusing on the aspects necessary for understanding how a lattice computation is performed and how discretization effects can be understood. Our work in Wilson and twisted-mass fermions investigates an increasingly relevant regime where lattice simulations are performed with quarks at or near their physical masses and both the mass difference of the up and down quarks and their differing electric charges are included. Our computation of a non-perturbative Greens functions on the lattice serves as a first attempt to validate recent work by Dine et. al. [24] in which they calculate Greens functions which vanish in perturbation theory, yet have a contribution from the one instanton background. In chapter 2, we determine the phase diagram and pion spectrum for Wilson and twisted-mass fermions in the presence of non-degeneracy between the up and down quark and discretization errors, using Wilson and twisted-mass chiral perturbation theory. We find that the CP-violating phase of the continuum theory (which occurs for sufficiently large non-degeneracy) is continuously connected to the Aoki phase of the lattice theory with degenerate quarks. We show that discretization effects can, in some cases, push simulations with physical masses closer to either the CP-violating phase or another phase not present in the continuum, so that at sufficiently large lattice spacings physical-point simulations could lie in one of these phases. In chapter 3, we extend the work in chapter 2 to include the effects of electromagnetism, so that it is applicable to recent simulations incorporating all sources of isospin breaking. For Wilson fermions, we find that the
Deflation of Eigenvalues for GMRES in Lattice QCD
International Nuclear Information System (INIS)
Morgan, Ronald B.; Wilcox, Walter
2002-01-01
Versions of GMRES with deflation of eigenvalues are applied to lattice QCD problems. Approximate eigenvectors corresponding to the smallest eigenvalues are generated at the same time that linear equations are solved. The eigenvectors improve convergence for the linear equations, and they help solve other right-hand sides
Volume dependence of light hadron masses in full lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Orth, B.; Lippert, T.; Schilling, K
2004-03-01
The aim of the GRAL project is to simulate full QCD with standard Wilson fermions at light quark masses on small to medium-sized lattices and to obtain infinite-volume results by extrapolation. In order to establish the functional form of the volume dependence we study systematically the finite-size effects in the light hadron spectrum. We give an update on the status of the GRAL project and show that our simulation data for the light hadron masses depend exponentially on the lattice size.
Volume dependence of light hadron masses in full lattice QCD
International Nuclear Information System (INIS)
Orth, B.; Lippert, T.; Schilling, K.
2004-01-01
The aim of the GRAL project is to simulate full QCD with standard Wilson fermions at light quark masses on small to medium-sized lattices and to obtain infinite-volume results by extrapolation. In order to establish the functional form of the volume dependence we study systematically the finite-size effects in the light hadron spectrum. We give an update on the status of the GRAL project and show that our simulation data for the light hadron masses depend exponentially on the lattice size
A transverse lattice QCD model for mesons
Energy Technology Data Exchange (ETDEWEB)
Patel, Apoorva D.; Ratabole, Raghunath
2004-03-01
QCD is analysed with two light-front continuum dimensions and two transverse lattice dimensions. In the limit of large number of colours and strong transverse gauge coupling, the contributions of light-front and transverse directions factorise in the dynamics, and the theory can be analytically solved in a closed form. An integral equation is obtained, describing the properties of mesons, which generalises the 't Hooft equation by including spin degrees of freedom. The meson spectrum, light-front wavefunctions and form factors can be obtained by solving this equation numerically. These results would be a good starting point to model QCD observables which only weakly depend on transverse directions, e.g. deep inelastic scattering structure functions.
Interquark potential with finite quark mass from lattice QCD.
Kawanai, Taichi; Sasaki, Shoichi
2011-08-26
We present an investigation of the interquark potential determined from the q ̄q Bethe-Salpeter (BS) amplitude for heavy quarkonia in lattice QCD. The q ̄q potential at finite quark mass m(q) can be calculated from the equal-time and Coulomb gauge BS amplitude through the effective Schrödinger equation. The definition of the potential itself requires information about a kinetic mass of the quark. We then propose a self-consistent determination of the quark kinetic mass on the same footing. To verify the proposed method, we perform quenched lattice QCD simulations with a relativistic heavy-quark action at a lattice cutoff of 1/a≈2.1 GeV in a range 1.0≤m(q)≤3.6 GeV. Our numerical results show that the q ̄q potential in the m(q)→∞ limit is fairly consistent with the conventional one obtained from Wilson loops. The quark-mass dependence of the q ̄q potential and the spin-spin potential are also examined. © 2011 American Physical Society
A scalable PC-based parallel computer for lattice QCD
International Nuclear Information System (INIS)
Fodor, Z.; Katz, S.D.; Pappa, G.
2003-01-01
A PC-based parallel computer for medium/large scale lattice QCD simulations is suggested. The Eoetvoes Univ., Inst. Theor. Phys. cluster consists of 137 Intel P4-1.7GHz nodes. Gigabit Ethernet cards are used for nearest neighbor communication in a two-dimensional mesh. The sustained performance for dynamical staggered (wilson) quarks on large lattices is around 70(110) GFlops. The exceptional price/performance ratio is below $1/Mflop
A scalable PC-based parallel computer for lattice QCD
International Nuclear Information System (INIS)
Fodor, Z.; Papp, G.
2002-09-01
A PC-based parallel computer for medium/large scale lattice QCD simulations is suggested. The Eoetvoes Univ., Inst. Theor. Phys. cluster consists of 137 Intel P4-1.7 GHz nodes. Gigabit Ethernet cards are used for nearest neighbor communication in a two-dimensional mesh. The sustained performance for dynamical staggered(wilson) quarks on large lattices is around 70(110) GFlops. The exceptional price/performance ratio is below $1/Mflop. (orig.)
Renormalisaton of composite operators in lattice QCD. Perturbative versus nonperturbative
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M.; Nakamura, Y. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics and Astronomy] (and others)
2010-07-01
The perturbative and nonperturbative renormalisation of quark-antiquark operators in lattice QCD with two flavours of clover fermions is investigated within the research programme of the QCDSF collaboration. Operators with up to three derivatives are considered. The nonperturbative results based on the RI-MOM scheme are compared with estimates from one- and two-loop lattice perturbation theory. (orig.)
Calculation of hadronic matrix elements using lattice QCD
International Nuclear Information System (INIS)
Gupta, R.
1993-01-01
The author gives a brief introduction to the scope of lattice QCD calculations in his effort to extract the fundamental parameters of the standard model. This goal is illustrated by two examples. First the author discusses the extraction of CKM matrix elements from measurements of form factors for semileptonic decays of heavy-light pseudoscalar mesons such as D → Keν. Second, he presents the status of results for the kaon B parameter relevant to CP violation. He concludes the talk with a short outline of his experiences with optimizing QCD codes on the CM5
Calculation of hadronic matrix elements using lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gupta, R.
1993-08-01
The author gives a brief introduction to the scope of lattice QCD calculations in his effort to extract the fundamental parameters of the standard model. This goal is illustrated by two examples. First the author discusses the extraction of CKM matrix elements from measurements of form factors for semileptonic decays of heavy-light pseudoscalar mesons such as D {yields} Ke{nu}. Second, he presents the status of results for the kaon B parameter relevant to CP violation. He concludes the talk with a short outline of his experiences with optimizing QCD codes on the CM5.
Prospects for N-N* Transitions from Lattice QCD
International Nuclear Information System (INIS)
Richards, David
2008-01-01
I describe the status of calculations of N-N* transition form factors in lattice QCD, and the prospects for future calculations. I emphasise the need to reliably delineate the states in the spectrum, and the progress that has been made by the Hadron Spectrum Collaboration in so doing.
Topological susceptibility in lattice QCD with unimproved Wilson fermions
International Nuclear Information System (INIS)
Chowdhury, Abhishek; De, Asit K.; De Sarkar, Sangita; Harindranath, A.; Mondal, Santanu; Sarkar, Anwesa; Maiti, Jyotirmoy
2012-01-01
We address a long standing problem regarding topology in lattice simulations of QCD with unimproved Wilson fermions. Earlier attempt with unimproved Wilson fermions at β=5.6 to verify the suppression of topological susceptibility with decreasing quark mass (m q ) was unable to unambiguously confirm the suppression. We carry out systematic calculations for two degenerate flavours at two different lattice spacings (β=5.6 and 5.8). The effects of quark mass, lattice volume and the lattice spacing on the spanning of different topological sectors are presented. We unambiguously demonstrate the suppression of the topological susceptibility with decreasing quark mass, expected from chiral Ward identity and chiral perturbation theory.
Hadronic matrix elements in lattice QCD
International Nuclear Information System (INIS)
Jaeger, Benjamin
2014-01-01
The lattice formulation of Quantum ChromoDynamics (QCD) has become a reliable tool providing an ab initio calculation of low-energy quantities. Despite numerous successes, systematic uncertainties, such as discretisation effects, finite-size effects, and contaminations from excited states, are inherent in any lattice calculation. Simulations with controlled systematic uncertainties and close to the physical pion mass have become state-of-the-art. We present such a calculation for various hadronic matrix elements using non-perturbatively O(a)-improved Wilson fermions with two dynamical light quark flavours. The main topics covered in this thesis are the axial charge of the nucleon, the electro-magnetic form factors of the nucleon, and the leading hadronic contributions to the anomalous magnetic moment of the muon. Lattice simulations typically tend to underestimate the axial charge of the nucleon by 5-10%. We show that including excited state contaminations using the summed operator insertion method leads to agreement with the experimentally determined value. Further studies of systematic uncertainties reveal only small discretisation effects. For the electro-magnetic form factors of the nucleon, we see a similar contamination from excited states as for the axial charge. The electro-magnetic radii, extracted from a dipole fit to the momentum dependence of the form factors, show no indication of finite-size or cutoff effects. If we include excited states using the summed operator insertion method, we achieve better agreement with the radii from phenomenology. The anomalous magnetic moment of the muon can be measured and predicted to very high precision. The theoretical prediction of the anomalous magnetic moment receives contribution from strong, weak, and electro-magnetic interactions, where the hadronic contributions dominate the uncertainties. A persistent 3σ tension between the experimental determination and the theoretical calculation is found, which is
Directory of Open Access Journals (Sweden)
Alexandrou Constantia
2017-01-01
Full Text Available We briefly discuss the current status of lattice QCD simulations and review selective results on nucleon observables focusing on recent developments in the lattice QCD evaluation of the nucleon form factors and radii, parton distribution functions and their moments, and the neutron electric dipole moment. Nucleon charges and moments of parton distribution functions are presented using simulations generated at physical values of the quark masses, while exploratory studies are performed for the parton distribution functions and the neutron electric dipole moment at heavier than physical value of the pion mass.
Lattice QCD at finite temperature and density from Taylor expansion
Steinbrecher, Patrick
2017-01-01
In the first part, I present an overview of recent Lattice QCD simulations at finite temperature and density. In particular, we discuss fluctuations of conserved charges: baryon number, electric charge and strangeness. These can be obtained from Taylor expanding the QCD pressure as a function of corresponding chemical potentials. Our simulations were performed using quark masses corresponding to physical pion mass of about 140 MeV and allow a direct comparison to experimental data from ultra-relativistic heavy ion beams at hadron colliders such as the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN. In the second part, we discuss computational challenges for current and future exascale Lattice simulations with a focus on new silicon developments from Intel and NVIDIA.
Gluon and ghost propagator studies in lattice QCD at finite temperature
International Nuclear Information System (INIS)
Aouane, Rafik
2013-01-01
Gluon and ghost propagators in quantum chromodynamics (QCD) computed in the infrared momentum region play an important role to understand quark and gluon confinement. They are the subject of intensive research thanks to non-perturbative methods based on Dyson-Schwinger (DS) and functional renormalization group (FRG) equations. Moreover, their temperature behavior might also help to explore the chiral and deconfinement phase transition or crossover within QCD at non-zero temperature. Our prime tool is the lattice discretized QCD (LQCD) providing a unique ab-initio non-perturbative approach to deal with the computation of various observables of the hadronic world. We investigate the temperature dependence of Landau gauge gluon and ghost propagators in pure gluodynamics and in full QCD. Regarding the gluon propagator, we compute its longitudinal D L as well its transversal D T components. The aim is to provide a data set in terms of fitting formulae which can be used as input for DS (or FRG) equations. We deal with full (N f =2) LQCD with the twisted mass fermion discretization. We employ gauge field configurations provided by the tmfT collaboration for temperatures in the crossover region and for three fixed pion mass values in the range [300,500] MeV. Finally, within SU(3) pure gauge theory (at T=0) we compute the Landau gauge gluon propagator according to different gauge fixing criteria. Our goal is to understand the influence of gauge copies with minimal (non-trivial) eigenvalues of the Faddeev-Popov operator.
A lattice QCD calculation of the transverse decay constant of the b{sub 1}(1235) meson
Energy Technology Data Exchange (ETDEWEB)
Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; McNeile, C. [Wuppertal Univ. (Germany). Theoretische Teilchenphysik; Michael, C. [Liverpool Univ. (United Kingdom). Theoretical Physics Division, Dept. of Mathematical Sciences; Urbach, C. [Humboldt-Univ., Berlin (Germany). Theorie der Elementarteilchen
2009-10-15
We review various B meson decays that require knowledge of the transverse decay constant of the b{sub 1}(1235) meson. We report on an exploratory lattice QCD calculation of the transverse decay constant of the b{sub 1} meson. The lattice QCD calculations used unquenched gauge configurations, at two lattice spacings, generated with two flavours of sea quarks. The twisted mass formalism is used. (orig.)
Chiral symmetry breaking and the Banks-Casher relation in lattice QCD with Wilson quarks
Giusti, Leonardo
2009-01-01
The Banks--Casher relation links the spontaneous breaking of chiral symmetry in QCD to the presence of a non-zero density of quark modes at the low end of the spectrum of the Dirac operator. Spectral observables like the number of modes in a given energy interval are renormalizable and can therefore be computed using the Wilson formulation of lattice QCD even though the latter violates chiral symmetry at energies on the order of the inverse lattice spacing. Using numerical simulations, we find (in two-flavour QCD) that the low quark modes do condense in the expected way. In particular, the chiral condensate can be accurately calculated simply by counting the low modes on large lattices. Other spectral observables can be considered as well and have a potentially wide range of uses.
Critical slowing down and error analysis in lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Stefan [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Sommer, Rainer; Virotta, Francesco [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2010-09-15
We study the critical slowing down towards the continuum limit of lattice QCD simulations with Hybrid Monte Carlo type algorithms. In particular for the squared topological charge we find it to be very severe with an effective dynamical critical exponent of about 5 in pure gauge theory. We also consider Wilson loops which we can demonstrate to decouple from the modes which slow down the topological charge. Quenched observables are studied and a comparison to simulations of full QCD is made. In order to deal with the slow modes in the simulation, we propose a method to incorporate the information from slow observables into the error analysis of physical observables and arrive at safer error estimates. (orig.)
Critical slowing down and error analysis in lattice QCD simulations
International Nuclear Information System (INIS)
Schaefer, Stefan; Sommer, Rainer; Virotta, Francesco
2010-09-01
We study the critical slowing down towards the continuum limit of lattice QCD simulations with Hybrid Monte Carlo type algorithms. In particular for the squared topological charge we find it to be very severe with an effective dynamical critical exponent of about 5 in pure gauge theory. We also consider Wilson loops which we can demonstrate to decouple from the modes which slow down the topological charge. Quenched observables are studied and a comparison to simulations of full QCD is made. In order to deal with the slow modes in the simulation, we propose a method to incorporate the information from slow observables into the error analysis of physical observables and arrive at safer error estimates. (orig.)
International Nuclear Information System (INIS)
Bitar, K.M.; Edwards, R.; Gottlieb, S.; Heller, U.M.; Kennedy, A.D.; Kim, S.; Kogut, J.B.; Krasnitz, A.; Liu, W.; Ogilvie, M.C.; Renken, R.L.; Sinclair, D.K.; Sugar, R.L.; Teper, M.; Toussaint, D.; Wang, K.C.
1993-01-01
The HTMCGC collaboration has been simulating lattice QCD with two light staggered quarks with masses m q = 0.0125 and also m q = 0.00625 on a 16 3 x 8 lattice. We have been studying the behaviour of the transition from hadronic matter to a quark-gluon plasma and the properties of that plasma. We have been measuring entropy densities, Debye and hadronic screening lengths, the spacial string tension and topological susceptibility in addition to the standard order parameters. The HEMCGC collaboration has simulated lattice QCD with two light staggered quarks, m q = 0.025 and m q = 0.010 on a 16 3 x 32 lattice. We have measured the glueball spectrum and topological susceptibilities for these runs. (orig.)
International Nuclear Information System (INIS)
Sinclair, D.K.
1992-01-01
The HTMCGC collaboration has been simulating lattice QCD with two light staggered quarks with masses m q = 0.0125 and also m q = 0.00625 on a 16 3 x 8 lattice. We have been studying the behavior of the transition from hadronic matter to a quark-gluon plasma and the properties of that plasma. We have been measuring entropy densities, Debye and hadronic screening lengths, the spacial string tension and topological susceptibility in addition to the standard order parameters. The HEMCGC collaboration has simulated lattice QCD with two light staggered quarks,m q = 0.025 and m q = 0.010 on a 16 3 x 32 lattice. We have measured the glueball spectrum and topological susceptibilities for these runs
Lattice QCD simulation of meson exchange forces
International Nuclear Information System (INIS)
Richards, D.G.; Sinclair, D.K.; Sivers, D.
1990-01-01
We present the formalism for investigating the bar Qq bar Qq system in lattice QCD. This system serves as a model for describing exchange forces between heavy, static hadrons. We use this formalism to calculate the exchange potential from gauge configurations which incorporate the effects of dynamical quarks. Our data can be interpreted as giving preliminary results on the range of the nuclear force
Lattice QCD at finite temperature with Wilson fermions
International Nuclear Information System (INIS)
Pinke, Christopher
2014-01-01
The subatomic world is governed by the strong interactions of quarks and gluons, described by Quantum Chromodynamics (QCD). Quarks experience confinement into colour-less objects, i.e. they can not be observed as free particles. Under extreme conditions such as high temperature or high density, this constraint softens and a transition to a phase where quarks and gluons are quasi-free particles (Quark-Gluon-Plasma) can occur. This environment resembles the conditions prevailing during the early stages of the universe shortly after the Big Bang. The phase diagram of QCD is under investigation in current and future collider experiments, for example at the Large Hadron Collider (LHC) or at the Facility for Antiproton and Ion Research (FAIR). Due to the strength of the strong interactions in the energy regime of interest, analytic methods can not be applied rigorously. The only tool to study QCD from first principles is given by simulations of its discretised version, Lattice QCD (LQCD). These simulations are in the high-performance computing area, hence, the numerical aspects of LQCD are a vital part in this field of research. In recent years, Graphic Processing Units (GPUs) have been incorporated in these simulations as they are a standard tool for general purpose calculations today. In the course of this thesis, the LQCD application CL 2 QCD has been developed, which allows for simulations on GPUs as well as on traditional CPUs, as it is based on OpenCL. CL 2 QCD constitutes the first application for Wilson type fermions in OpenCL. It provides excellent performance and has been applied in physics studies presented in this thesis. The investigation of the QCD phase diagram is hampered by the notorious sign-problem, which restricts current simulation algorithms to small values of the chemical potential. Theoretically, studying unphysical parameter ranges allows for constraints on the phase diagram. Of utmost importance is the clarification of the order of the finite
Polynomial hybrid Monte Carlo algorithm for lattice QCD with an odd number of flavors
International Nuclear Information System (INIS)
Aoki, S.; Burkhalter, R.; Ishikawa, K-I.; Tominaga, S.; Fukugita, M.; Hashimoto, S.; Kaneko, T.; Kuramashi, Y.; Okawa, M.; Tsutsui, N.; Yamada, N.; Ishizuka, N.; Iwasaki, Y.; Kanaya, K.; Ukawa, A.; Yoshie, T.; Onogi, T.
2002-01-01
We present a polynomial hybrid Monte Carlo (PHMC) algorithm for lattice QCD with odd numbers of flavors of O(a)-improved Wilson quark action. The algorithm makes use of the non-Hermitian Chebyshev polynomial to approximate the inverse square root of the fermion matrix required for an odd number of flavors. The systematic error from the polynomial approximation is removed by a noisy Metropolis test for which a new method is developed. Investigating the property of our PHMC algorithm in the N f =2 QCD case, we find that it is as efficient as the conventional HMC algorithm for a moderately large lattice size (16 3 x48) with intermediate quark masses (m PS /m V ∼0.7-0.8). We test our odd-flavor algorithm through extensive simulations of two-flavor QCD treated as an N f =1+1 system, and comparing the results with those of the established algorithms for N f =2 QCD. These tests establish that our PHMC algorithm works on a moderately large lattice size with intermediate quark masses (16 3 x48,m PS /m V ∼0.7-0.8). Finally we experiment with the (2+1)-flavor QCD simulation on small lattices (4 3 x8 and 8 3 x16), and confirm the agreement of our results with those obtained with the R algorithm and extrapolated to a zero molecular dynamics step size
A Framework for Lattice QCD Calculations on GPUs
Energy Technology Data Exchange (ETDEWEB)
Winter, Frank; Clark, M A; Edwards, Robert G; Joo, Balint
2014-08-01
Computing platforms equipped with accelerators like GPUs have proven to provide great computational power. However, exploiting such platforms for existing scientific applications is not a trivial task. Current GPU programming frameworks such as CUDA C/C++ require low-level programming from the developer in order to achieve high performance code. As a result porting of applications to GPUs is typically limited to time-dominant algorithms and routines, leaving the remainder not accelerated which can open a serious Amdahl's law issue. The lattice QCD application Chroma allows to explore a different porting strategy. The layered structure of the software architecture logically separates the data-parallel from the application layer. The QCD Data-Parallel software layer provides data types and expressions with stencil-like operations suitable for lattice field theory and Chroma implements algorithms in terms of this high-level interface. Thus by porting the low-level layer one can effectively move the whole application in one swing to a different platform. The QDP-JIT/PTX library, the reimplementation of the low-level layer, provides a framework for lattice QCD calculations for the CUDA architecture. The complete software interface is supported and thus applications can be run unaltered on GPU-based parallel computers. This reimplementation was possible due to the availability of a JIT compiler (part of the NVIDIA Linux kernel driver) which translates an assembly-like language (PTX) to GPU code. The expression template technique is used to build PTX code generators and a software cache manages the GPU memory. This reimplementation allows us to deploy an efficient implementation of the full gauge-generation program with dynamical fermions on large-scale GPU-based machines such as Titan and Blue Waters which accelerates the algorithm by more than an order of magnitude.
Vector and scalar charmonium resonances with lattice QCD
International Nuclear Information System (INIS)
Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa
2015-01-01
We perform an exploratory lattice QCD simulation of DD¯ scattering, aimed at determining the masses as well as the decay widths of charmonium resonances above open charm threshold. Neglecting coupling to other channels, the resulting phase shift for DD¯ scattering in p-wave yields the well-known vector resonance ψ(3770). For m π = 156 MeV, the extracted resonance mass and the decay width agree with experiment within large statistical uncertainty. The scalar charmonium resonances present a puzzle, since only the ground state χ c0 (1P) is well understood, while there is no commonly accepted candidate for its first excitation. We simulate DD¯ scattering in s-wave in order to shed light on this puzzle. The resulting phase shift supports the existence of a yet-unobserved narrow resonance with a mass slightly below 4 GeV. A scenario with this narrow resonance and a pole at χ c0 (1P) agrees with the energy-dependence of our phase shift. In addition, further lattice QCD simulations and experimental efforts are needed to resolve the puzzle of the excited scalar charmonia
Renormalization of Supersymmetric QCD on the Lattice
Costa, Marios; Panagopoulos, Haralambos
2018-03-01
We perform a pilot study of the perturbative renormalization of a Supersymmetric gauge theory with matter fields on the lattice. As a specific example, we consider Supersymmetric N=1 QCD (SQCD). We study the self-energies of all particles which appear in this theory, as well as the renormalization of the coupling constant. To this end we compute, perturbatively to one-loop, the relevant two-point and three-point Green's functions using both dimensional and lattice regularizations. Our lattice formulation involves theWilson discretization for the gluino and quark fields; for gluons we employ the Wilson gauge action; for scalar fields (squarks) we use naive discretization. The gauge group that we consider is SU(Nc), while the number of colors, Nc, the number of flavors, Nf, and the gauge parameter, α, are left unspecified. We obtain analytic expressions for the renormalization factors of the coupling constant (Zg) and of the quark (ZΨ), gluon (Zu), gluino (Zλ), squark (ZA±), and ghost (Zc) fields on the lattice. We also compute the critical values of the gluino, quark and squark masses. Finally, we address the mixing which occurs among squark degrees of freedom beyond tree level: we calculate the corresponding mixing matrix which is necessary in order to disentangle the components of the squark field via an additional finite renormalization.
Extracting scattering phase shifts in higher partial waves from lattice QCD calculations
Energy Technology Data Exchange (ETDEWEB)
Luu, Thomas; Savage, Martin J.
2011-06-01
Lüscher’s method is routinely used to determine meson-meson, meson-baryon, and baryon-baryon s-wave scattering amplitudes below inelastic thresholds from lattice QCD calculations—presently at unphysical light-quark masses. In this work we review the formalism and develop the requisite expressions to extract phase shifts describing meson-meson scattering in partial waves with angular momentum l≤6 and l=9. The implications of the underlying cubic symmetry, and strategies for extracting the phase shifts from lattice QCD calculations, are presented, along with a discussion of the signal-to-noise problem that afflicts the higher partial waves.
International Nuclear Information System (INIS)
Levi, A.R.; Lubicz, V.; Rebbi, C.
1997-01-01
We discuss a general strategy to compute the coefficients of the QCD chiral Lagrangian using lattice QCD with Wilson fermions. This procedure requires the introduction of a lattice chiral Lagrangian as an intermediate step in the calculation. The QCD chiral Lagrangian is then obtained by expanding the lattice effective theory in increasing powers of the lattice spacing and the external momenta. In order to investigate the general structure of the lattice effective Lagrangian, we perform an analytical calculation at the leading order of the strong-coupling and large-N expansion. We find that the explicit chiral symmetry breaking, introduced on the lattice by the Wilson term, is reproduced in the effective theory by a set of additional terms, which do not have direct correspondence in the continuum chiral Lagrangian. We argue that these terms can be conveniently reabsorbed by a suitable renormalization procedure. This is shown explicitly at the leading order of the strong-coupling and large-N expansion. In fact, we find that at this order, as is known to be the case in the opposite weak-coupling limit, the vector and axial Ward identities of the continuum theory are reproduced on the lattice provided that the bare quark mass and the lattice operators are properly renormalized. copyright 1997 The American Physical Society
Lattice QCD studies on baryon interactions in the strangeness -2 sector with physical quark masses
Sasaki, Kenji; Aoki, Sinya; Doi, Takumi; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Miyamoto, Takaya
2018-03-01
We investigate baryon-baryon (BB) interactions in the strangeness S = -2 sector via the coupled-channel HAL QCD method which enables us to extract the scattering observables from Nambu-Bethe-Salpeter (NBS) wave function on the lattice. The simulations are performed with (almost) physical quark masses (mπ = 146MeV) and a huge lattice volume of La = 8.1fm. We discuss the fate of H-dibaryon state through the ΛΛ and NΞ coupled-channel scatterings
Lattice QCD and b Physics - a 2006 Update
International Nuclear Information System (INIS)
Davies, C.T.H.
2007-01-01
Realistic lattice QCD calculations, including the effects of up, down and strange sea quarks, are maturing and continued comparison against experiment is consolidating the confidence we can place in the results. I will review in particular the latest results in bottom and charm physics and what the near future holds for the numbers needed for the B physics programme
Wilson Dslash Kernel From Lattice QCD Optimization
Energy Technology Data Exchange (ETDEWEB)
Joo, Balint [Jefferson Lab, Newport News, VA; Smelyanskiy, Mikhail [Parallel Computing Lab, Intel Corporation, California, USA; Kalamkar, Dhiraj D. [Parallel Computing Lab, Intel Corporation, India; Vaidyanathan, Karthikeyan [Parallel Computing Lab, Intel Corporation, India
2015-07-01
Lattice Quantum Chromodynamics (LQCD) is a numerical technique used for calculations in Theoretical Nuclear and High Energy Physics. LQCD is traditionally one of the first applications ported to many new high performance computing architectures and indeed LQCD practitioners have been known to design and build custom LQCD computers. Lattice QCD kernels are frequently used as benchmarks (e.g. 168.wupwise in the SPEC suite) and are generally well understood, and as such are ideal to illustrate several optimization techniques. In this chapter we will detail our work in optimizing the Wilson-Dslash kernels for Intel Xeon Phi, however, as we will show the technique gives excellent performance on regular Xeon Architecture as well.
Gluon and ghost propagator studies in lattice QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Aouane, Rafik
2013-04-29
Gluon and ghost propagators in quantum chromodynamics (QCD) computed in the infrared momentum region play an important role to understand quark and gluon confinement. They are the subject of intensive research thanks to non-perturbative methods based on Dyson-Schwinger (DS) and functional renormalization group (FRG) equations. Moreover, their temperature behavior might also help to explore the chiral and deconfinement phase transition or crossover within QCD at non-zero temperature. Our prime tool is the lattice discretized QCD (LQCD) providing a unique ab-initio non-perturbative approach to deal with the computation of various observables of the hadronic world. We investigate the temperature dependence of Landau gauge gluon and ghost propagators in pure gluodynamics and in full QCD. Regarding the gluon propagator, we compute its longitudinal D{sub L} as well its transversal D{sub T} components. The aim is to provide a data set in terms of fitting formulae which can be used as input for DS (or FRG) equations. We deal with full (N{sub f}=2) LQCD with the twisted mass fermion discretization. We employ gauge field configurations provided by the tmfT collaboration for temperatures in the crossover region and for three fixed pion mass values in the range [300,500] MeV. Finally, within SU(3) pure gauge theory (at T=0) we compute the Landau gauge gluon propagator according to different gauge fixing criteria. Our goal is to understand the influence of gauge copies with minimal (non-trivial) eigenvalues of the Faddeev-Popov operator.
Improved actions for QCD thermodynamics on the lattice
Beinlich, B; Laermann, E
1996-01-01
Finite cut-off effects strongly influence the thermodynamics of lattice regularized QCD at high temperature in the standard Wilson formulation. We analyze the reduction of finite cut-off effects in formulations of the thermodynamics of SU(N) gauge theories with three different O(a^2) and O(a^4) improved actions. We calculate the energy density and pressure on finite lattices in leading order weak coupling perturbation theory (T\\rightarrow \\infty) and perform Monte Carlo simulations with improved SU(3) actions at non-zero g^2. Already on lattices with temporal extent N_\\tau=4 we find a strong reduction of finite cut-off effects in the high temperature limit, which persists also down to temperatures a few times the deconfinement transition temperature.
Mirage in temporal correlation functions for baryon-baryon interactions in lattice QCD
International Nuclear Information System (INIS)
Iritani, T.; Doi, T.; Aoki, S.; Gongyo, S.; Hatsuda, T.; Ikeda, Y.; Inoue, T.; Ishii, N.; Murano, K.; Nemura, H.; Sasaki, K.
2016-01-01
Single state saturation of the temporal correlation function is a key condition to extract physical observables such as energies and matrix elements of hadrons from lattice QCD simulations. A method commonly employed to check the saturation is to seek for a plateau of the observables for large Euclidean time. Identifying the plateau in the cases having nearby states, however, is non-trivial and one may even be misled by a fake plateau. Such a situation takes place typically for a system with two or more baryons. In this study, we demonstrate explicitly the danger from a possible fake plateau in the temporal correlation functions mainly for two baryons (ΞΞ and NN), and three and four baryons ("3He and "4He) as well, employing (2+1)-flavor lattice QCD at m_π=0.51 GeV on four lattice volumes with L= 2.9, 3.6, 4.3 and 5.8 fm. Caution is required when drawing conclusions about the bound NN, 3N and 4N systems based only on the standard plateau fitting of the temporal correlation functions.
Pion structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Javadi Motaghi, Narjes
2015-05-12
In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.
Lattice QCD and the Schwarz alternating procedure
Lüscher, Martin
2003-01-01
A numerical simulation algorithm for lattice QCD is described, in which the short- and long-distance effects of the sea quarks are treated separately. The algorithm can be regarded, to some extent, as an implementation at the quantum level of the classical Schwarz alternating procedure for the solution of elliptic partial differential equations. No numerical tests are reported here, but theoretical arguments suggest that the algorithm should work well also at small quark masses.
Lattice QCD studies on baryon interactions in the strangeness -2 sector with physical quark masses
Directory of Open Access Journals (Sweden)
Sasaki Kenji
2018-01-01
Full Text Available We investigate baryon-baryon (BB interactions in the strangeness S = −2 sector via the coupled-channel HAL QCD method which enables us to extract the scattering observables from Nambu-Bethe-Salpeter (NBS wave function on the lattice. The simulations are performed with (almost physical quark masses (mπ = 146MeV and a huge lattice volume of La = 8.1fm. We discuss the fate of H-dibaryon state through the ΛΛ and NΞ coupled-channel scatterings
Chiral symmetry breaking and cooling in lattice QCD
International Nuclear Information System (INIS)
Woloshyn, R.M.; Lee, F.X.
1995-08-01
Chiral symmetry breaking is calculated as a function of cooling in quenched lattice QCD. A non-zero signal is found for the chiral condensate beyond one hundred cooling steps, suggesting that there is chiral symmetry breaking associated with instantons. Quantitatively, the chiral condensate in cooled gauge field configurations is small compared to the value without cooling. (author) 7 refs., 1 tab., 3 figs
Benchmark test of CP-PACS for lattice QCD
International Nuclear Information System (INIS)
Yoshie, Tomoteru
1996-01-01
The CP-PACS is a massively parallel computer dedicated for calculations in computational physics and will be in operation in the spring of 1996 at Center for Computational Physics, University of Tsukuba. In this paper, we describe the architecture of the CP-PACS and report the results of the estimate of the performance of the CP-PACS for typical lattice QCD calculations. (author)
The static-light meson spectrum from twisted mass lattice QCD
International Nuclear Information System (INIS)
Jansen, Karl; Michael, Chris; Shindler, Andrea; Wagner, Marc
2008-10-01
We compute the static-light meson spectrum with N f =2 flavours of sea quarks using Wilson twisted mass lattice QCD. We consider five different values for the light quark mass corresponding to 300 MeV PS s mesons. (orig.)
A new simulation algorithm for lattice QCD with dynamical quarks
Bunk, B.; Jegerlehner, B.; Luscher, M.; Simma, H.; Sommer, R.; Bunk, B; Jansen, K; Jegerlehner, B; Luscher, M; Simma, H
1994-01-01
A previously introduced multi-boson technique for the simulation of QCD with dynamical quarks is described and some results of first test runs on a 6^3\\times12 lattice with Wilson quarks and gauge group SU(2) are reported.
Observations on discretization errors in twisted-mass lattice QCD
International Nuclear Information System (INIS)
Sharpe, Stephen R.
2005-01-01
I make a number of observations concerning discretization errors in twisted-mass lattice QCD that can be deduced by applying chiral perturbation theory including lattice artifacts. (1) The line along which the partially conserved axial current quark mass vanishes in the untwisted-mass-twisted-mass plane makes an angle to the twisted-mass axis which is a direct measure of O(a) terms in the chiral Lagrangian, and is found numerically to be large; (2) Numerical results for pionic quantities in the mass plane show the qualitative properties predicted by chiral perturbation theory, in particular, an asymmetry in slopes between positive and negative untwisted quark masses; (3) By extending the description of the 'Aoki regime' (where m q ∼a 2 Λ QCD 3 ) to next-to-leading order in chiral perturbation theory I show how the phase-transition lines and lines of maximal twist (using different definitions) extend into this region, and give predictions for the functional form of pionic quantities; (4) I argue that the recent claim that lattice artifacts at maximal twist have apparent infrared singularities in the chiral limit results from expanding about the incorrect vacuum state. Shifting to the correct vacuum (as can be done using chiral perturbation theory) the apparent singularities are summed into nonsingular, and furthermore predicted, forms. I further argue that there is no breakdown in the Symanzik expansion in powers of lattice spacing, and no barrier to simulating at maximal twist in the Aoki regime
Nucleon structure by Lattice QCD computations with twisted mass fermions
International Nuclear Information System (INIS)
Harraud, P.A.
2010-11-01
Understanding the structure of the nucleon from quantum chromodynamics (QCD) is one of the greatest challenges of hadronic physics. Only lattice QCD allows to determine numerically the values of the observables from ab-initio principles. This thesis aims to study the nucleon form factors and the first moments of partons distribution functions by using a discretized action with twisted mass fermions. As main advantage, the discretization effects are suppressed at first order in the lattice spacing. In addition, the set of simulations allows a good control of the systematical errors. After reviewing the computation techniques, the results obtained for a wide range of parameters are presented, with lattice spacings varying from 0.0056 fm to 0.089 fm, spatial volumes from 2.1 up to 2.7 fm and several pion masses in the range of 260-470 MeV. The vector renormalization constant was determined in the nucleon sector with improved precision. Concerning the electric charge radius, we found a finite volume effect that provides a key towards an explanation of the chiral dependence of the physical point. The results for the magnetic moment, the axial charge, the magnetic and axial charge radii, the momentum and spin fractions carried by the quarks show no dependence on the lattice spacing nor volume. In our range of pion masses, their values show a deviation from the experimental values. Their chiral behaviour do not exhibit the curvature predicted by the chiral perturbation theory which could explain the apparent discrepancy. (author)
From hot lattice QCD to cold quark stars
International Nuclear Information System (INIS)
Schulze, Robert
2011-01-01
A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)
From hot lattice QCD to cold quark stars
Energy Technology Data Exchange (ETDEWEB)
Schulze, Robert
2011-02-22
A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)
The nucleon mass and pion-nucleon sigma term from a chiral analysis of Nf = 2 lattice QCD world data
Directory of Open Access Journals (Sweden)
Alvarez-Ruso L.
2014-03-01
Full Text Available We investigate the pion-mass dependence of the nucleon mass within the covariant SU(2 baryon chiral perturbation theory up to order p4 with and without explicit Δ (1232 degrees of freedom. We fit lattice QCD data from several collaborations for 2 and 2+1 flavor ensembles. Here, we emphasize our Nf = 2 study where the inclusion the Δ (1232 contributions stabilizes the fits. We correct for finite volume and spacing effects, set independently the lattice QCD scale by a Sommer-scale of r0 = 0.493(23 fm and also include one σπN lQCD data point at Mπ ≈ 290 MeV. We obtain low-energy constants of natural size which are compatible with the rather linear pion-mass dependence observed in lattice QCD. We report a value of σπN = 41(5(4 MeV for the 2 flavor case and σπN = 52(3(8 MeV for 2+1 flavors.
Meson Correlators in Finite Temperature Lattice QCD
De Forcrand, Philippe; Hashimoto, T; Hioki, S; Matsufuru, H; Miyamura, O; Nakamura, A; Takaishi, T; Umeda, T; Stamatescu, I O; CERN. Geneva; Forcrand, Ph. de
2001-01-01
We analyze temporal and spatial meson correlators in quenched lattice QCD at T>0. Below T_c we observe little change in the meson properties as compared with T=0. Above T_c we observe new features: chiral symmetry restoration and signals of plasma formation, but also indication of persisting mesonic (metastable) states and different temporal and spatial masses in the mesonic channels. This suggests a complex picture of QGP in the region 1 - 1.5 T_c.
Charmed meson decay constants in three-flavor lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Aubin, C.; Bernard, C.; DeTar, C.; Di Pierro, M.; Freeland, Elizabeth D.; Gottlieb, Steven; Heller, U.M.; Hetrick, J.E.; El-Khadra, Aida X.; Kronfeld, Andreas S.; Levkova, L.; Mackenzie, P.B.; Menscher, D.; Maresca, F.; Nobes, M.; Okamoto, M.; Renner, D.B.; Simone, J.; Sugar, R.; Toussaint, D.; Trottier, H.D.; /Art Inst. of Chicago /Columbia
2005-06-01
The authors present the first lattice QCD calculation with realistic sea quark content of the D{sup +}-meson decay constant f{sub D+}. They use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). They obtain f{sub D+} = 201 {+-} 3 {+-} 17 MeV, where the errors are statistical and a combination of systematic errors. They also obtain f{sub D{sub s}} = 249 {+-} 3 {+-} 16 MeV for the D{sub s} meson.
D-Meson Mixing in 2+1-Flavor Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Chang, Chia Cheng [William-Mary Coll.; Bouchard, C. M. [William-Mary Coll.; El-Khadra, A. X. [Illinois U., Urbana; Freeland, E. [Art Inst. of Chicago; Gámiz, E. [Granada U., Theor. Phys. Astrophys.; Kronfeld, A. S. [Fermilab; Laiho, J. W. [Syracuse U.; Neil, E. T. [Colorado U.; Simone, J. N. [Fermilab; Van de Water, R. S. [Fermilab
2017-01-20
We present results for neutral D-meson mixing in 2+1-flavor lattice QCD. We compute the matrix elements for all five operators that contribute to D mixing at short distances, including those that only arise beyond the Standard Model. Our results have an uncertainty similar to those of the ETM collaboration (with 2 and with 2+1+1 flavors). This work shares many features with a recent publication on B mixing and with ongoing work on heavy-light decay constants from the Fermilab Lattice and MILC Collaborations.
Nucleon electromagnetic form factors in twisted mass lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Guichon, P.; Jansen, K.; Korzec, T.; Constantinou, M.
2011-01-01
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cutoff effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment.
Two-nucleon bound states in quenched lattice QCD
International Nuclear Information System (INIS)
Yamazaki, T.; Kuramashi, Y.; Ukawa, A.
2011-01-01
We address the issue of bound state in the two-nucleon system in lattice QCD. Our study is made in the quenched approximation at the lattice spacing of a=0.128 fm with a heavy quark mass corresponding to m π =0.8 GeV. To distinguish a bound state from an attractive scattering state, we investigate the volume dependence of the energy difference between the ground state and the free two-nucleon state by changing the spatial extent of the lattice from 3.1 fm to 12.3 fm. A finite energy difference left in the infinite spatial volume limit leads us to the conclusion that the measured ground states for not only spin triplet but also singlet channels are bounded. Furthermore the existence of the bound state is confirmed by investigating the properties of the energy for the first excited state obtained by a 2x2 diagonalization method. The scattering lengths for both channels are evaluated by applying the finite volume formula derived by Luescher to the energy of the first excited states.
Spectral functions from anisotropic lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Aarts, G.; Allton, C. [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Amato, A. [Helsinki Institute of Physics and University of Helsinki, Helsinki (Finland); Evans, W. [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics Universitat Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Giudice, P. [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, T. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kelly, A. [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Kim, S.Y. [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, M.P. [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Praki, K. [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Ryan, S.M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Skullerud, J.-I. [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland)
2016-12-15
The FASTSUM collaboration has been carrying out lattice simulations of QCD for temperatures ranging from one third to twice the crossover temperature, investigating the transition region, as well as the properties of the Quark Gluon Plasma. In this contribution we concentrate on quarkonium correlators and spectral functions. We work in a fixed scale scheme and use anisotropic lattices which help achieving the desirable fine resolution in the temporal direction, thus facilitating the (ill posed) integral transform from imaginary time to frequency space. We contrast and compare results for the correlators obtained with different methods, and different temporal spacings. We observe robust features of the results, confirming the sequential dissociation scenario, but also quantitative differences indicating that the methods' systematic errors are not yet under full control. We briefly outline future steps towards accurate results for the spectral functions and their associated statistical and systematic errors.
Field strength correlators in QCD: new fits to the lattice data
International Nuclear Information System (INIS)
Meggiolaro, E.
1999-01-01
We discuss the results obtained by fitting the lattice data of the gauge-invariant field strength correlators in QCD with some particular functions which are commonly used in the literature in some phenomenological approaches to high-energy hadron-hadron scattering. A comparison is done with the results obtained in the original fits to the lattice data. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)
Strong coupling constant from Adler function in lattice QCD
Hudspith, Renwick J.; Lewis, Randy; Maltman, Kim; Shintani, Eigo
2016-09-01
We compute the QCD coupling constant, αs, from the Adler function with vector hadronic vacuum polarization (HVP) function. On the lattice, Adler function can be measured by the differential of HVP at two different momentum scales. HVP is measured from the conserved-local vector current correlator using nf = 2 + 1 flavor Domain Wall lattice data with three different lattice cutoffs, up to a-1 ≈ 3.14 GeV. To avoid the lattice artifact due to O(4) symmetry breaking, we set the cylinder cut on the lattice momentum with reflection projection onto vector current correlator, and it then provides smooth function of momentum scale for extracted HVP. We present a global fit of the lattice data at a justified momentum scale with three lattice cutoffs using continuum perturbation theory at 𝒪(αs4) to obtain the coupling in the continuum limit at arbitrary scale. We take the running to Z boson mass through the appropriate thresholds, and obtain αs(5)(MZ) = 0.1191(24)(37) where the first is statistical error and the second is systematic one.
First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints
Lin, H.-W.; Melnitchouk, W.; Prokudin, A.; Sato, N.; Shows, H.; Jefferson Lab Angular Momentum JAM Collaboration
2018-04-01
We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor charge gT from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with gT values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller gT values. The contributions to the nucleon tensor charge from u and d quarks are found to be δ u =0.3 (2 ) and δ d =-0.7 (2 ) at a scale Q2=2 GeV2.
fB from finite size effects in lattice QCD
International Nuclear Information System (INIS)
Guagnelli, M.; Palombi, F.; Petronzio, R.; Tantalo, N.
2003-01-01
We discuss a novel method to calculate f B on the lattice, introduced in [1], based on the study of the dependence of finite size effects upon the heavy quark mass of flavoured mesons and on a non-perturbative recursive finite size technique. This method avoids the systematic errors related to extrapolations from the static limit or to the tuning of the coefficients of effective Lagrangian and the results admit an extrapolation to the continuum limit. We show the results of a first estimate at finite lattice spacing, but close to the continuum limit, giving f B = 170(11)(5)(22) MeV. We also obtain f B s = 192(9)(5)(24)MeV. The first error is statistical, the second is our estimate of the systematic error from the method and the third the systematic error from the specific approximations adopted in this first exploratory calculation. The method can be generalized to two-scale problems in lattice QCD
Nucleon wave function from lattice QCD
International Nuclear Information System (INIS)
Warkentin, Nikolaus
2008-04-01
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Nucleon wave function from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Warkentin, Nikolaus
2008-04-15
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method
Iritani, T.; HAL QCD Collaboration
We make a detailed comparison between the direct method and the HAL QCD potential method for the baryon-baryon interactions, taking the $\\Xi\\Xi$ system at $m_\\pi= 0.51$ GeV in 2+1 flavor QCD and using both smeared and wall quark sources. The energy shift $\\Delta E_\\mathrm{eff}(t)$ in the direct method shows the strong dependence on the choice of quark source operators, which means that the results with either (or both) source are false. The time-dependent HAL QCD method, on the other hand, gives the quark source independent $\\Xi\\Xi$ potential, thanks to the derivative expansion of the potential, which absorbs the source dependence to the next leading order correction. The HAL QCD potential predicts the absence of the bound state in the $\\Xi\\Xi$($^1$S$_0$) channel at $m_\\pi= 0.51$ GeV, which is also confirmed by the volume dependence of finite volume energy from the potential. We also demonstrate that the origin of the fake plateau in the effective energy shift $\\Delta E_\\mathrm{eff}(t)$ at $t \\sim 1$ fm can be clarified by a few low-lying eigenfunctions and eigenvalues on the finite volume derived from the HAL QCD potential, which implies that the ground state saturation of $\\Xi\\Xi$($^1$S$_0$) requires $t \\sim 10$ fm in the direct method for the smeared source on $(4.3 \\ \\mathrm{fm})^3$ lattice, while the HAL QCD method does not suffer from such a problem.
Monte Carlo numerical study of lattice field theories
International Nuclear Information System (INIS)
Gan Cheekwan; Kim Seyong; Ohta, Shigemi
1997-01-01
The authors are interested in the exact first-principle calculations of quantum field theories which are indeed exact ones. For quantum chromodynamics (QCD) at low energy scale, a nonperturbation method is needed, and the only known such method is the lattice method. The path integral can be evaluated by putting a system on a finite 4-dimensional volume and discretizing space time continuum into finite points, lattice. The continuum limit is taken by making the lattice infinitely fine. For evaluating such a finite-dimensional integral, the Monte Carlo numerical estimation of the path integral can be obtained. The calculation of light hadron mass in quenched lattice QCD with staggered quarks, 3-dimensional Thirring model calculation and the development of self-test Monte Carlo method have been carried out by using the RIKEN supercomputer. The motivation of this study, lattice QCD formulation, continuum limit, Monte Carlo update, hadron propagator, light hadron mass, auto-correlation and source size dependence are described on lattice QCD. The phase structure of the 3-dimensional Thirring model for a small 8 3 lattice has been mapped. The discussion on self-test Monte Carlo method is described again. (K.I.)
Spectroscopy of doubly charmed baryons from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Padmanath, M. [Univ. of Graz, Graz (Austria); Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Mathur, Nilmani [Tata Inst. of Fundamental Research, Mumbai (India); Peardon, Michael [Trinity College, Dublin (Ireland)
2015-05-06
This study presents the ground and excited state spectra of doubly charmed baryons from lattice QCD with dynamical quark fields. Calculations are performed on anisotropic lattices of size 16³ × 128, with inverse spacing in temporal direction a_{t}⁻¹=5.67(4) GeV and with a pion mass of about 390 MeV. A large set of baryonic operators that respect the symmetries of the lattice yet which retain a memory of their continuum analogues are used. These operators transform as irreducible representations of SU(3)_{F} symmetry for flavor, SU(4) symmetry for Dirac spins of quarks and O(3) for spatial symmetry. The distillation method is utilized to generate baryon correlation functions which are analyzed using the variational fitting method to extract excited states. The lattice spectra obtained have baryonic states with well-defined total spins up to 7/2 and the pattern of low-lying states does not support the diquark picture for doubly charmed baryons. On the contrary the calculated spectra are remarkably similar to the expectations from models with an SU(6)×O(3) symmetry. Various spin-dependent energy splittings between the extracted states are also evaluated.
Δ(1232) Axial Charge and Form Factors from Lattice QCD
International Nuclear Information System (INIS)
Alexandrou, Constantia; Gregory, Eric B.; Korzec, Tomasz; Koutsou, Giannis; Negele, John W.; Sato, Toru; Tsapalis, Antonios
2011-01-01
We present the first calculation on the Δ axial vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axial charge, N to Δ axial transition coupling constant and Δ axial charge.
Beauty and the beast: What lattice QCD can do for B physics
International Nuclear Information System (INIS)
Kronfeld, A.S.
1993-01-01
One of the reasons why b-hadrons are interesting is that their properties (decays, mixing, CP violation) help determine the least well-known elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. In each case, however, the standard-model expression for the (differential) decay rate follows the pattern: (experimental measurement) = (known factors)(QCD factor)(CKM factor). To extract the CKM factor from the measurement one must have reliable theoretical calculations in nonperturbative QCD. The only systematic, first-principles approach to nonperturbative QCD is the formulation on the lattice. The most promising calculational method has proven to be large-scale numerical computations
Bootstrap bound for conformal multi-flavor QCD on lattice
Energy Technology Data Exchange (ETDEWEB)
Nakayama, Yu [Department of Physics, Rikkyo University,Toshima, Tokyo 171-8501 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo,5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)
2016-07-08
The recent work by Iha et al. shows an upper bound on mass anomalous dimension γ{sub m} of multi-flavor massless QCD at the renormalization group fixed point from the conformal bootstrap in SU(N{sub F}){sub V} symmetric conformal field theories under the assumption that the fixed point is realizable with the lattice regularization based on staggered fermions. We show that the almost identical but slightly stronger bound applies to the regularization based on Wilson fermions (or domain wall fermions) by studying the conformal bootstrap in SU(N{sub f}){sub L}×SU(N{sub f}){sub R} symmetric conformal field theories. For N{sub f}=8, our bound implies γ{sub m}<1.31 to avoid dangerously irrelevant operators that are not compatible with the lattice symmetry.
Nucleon electromagnetic form factors in twisted mass lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Jansen, K.; Korzec, T.; Humboldt Univ. Berlin
2011-02-01
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment. (orig.)
Polarized and unpolarized nucleon structure functions from lattice QCD
International Nuclear Information System (INIS)
Goeckeler, M.; Technische Hochschule Aachen; Horsley, R.; Humboldt-Universitaet, Berlin; Ilgenfritz, E.M.; Perlt, H.; Rakow, P.; Schierholz, G.; Forschungszentrum Juelich GmbH; Schiller, A.
1995-06-01
We report on a high statistics quenched lattice QCD calculation of the deep-inelastic structure functions F 1 , F 2 , g 1 and g 2 of the proton and neutron. The theoretical basis for the calculation is the operator product expansion. We consider the moments of the leading twist operators up to spin four. Using Wilson fermions the calculation is done for three values of K, and we perform the extrapolation to the chiral limit. The renormalization constants, which lead us from lattice to continuum operators, are calculated in perturbation theory to one loop order. (orig.)
Light meson form factors at high Q2 from lattice QCD
Koponen, Jonna; Zimermmane-Santos, André; Davies, Christine; Lepage, G. Peter; Lytle, Andrew
2018-03-01
Measurements and theoretical calculations of meson form factors are essential for our understanding of internal hadron structure and QCD, the dynamics that bind the quarks in hadrons. The pion electromagnetic form factor has been measured at small space-like momentum transfer |q2| theory is applicable. This leaves a gap in the intermediate Q2 where the form factors are not known. As a part of their 12 GeV upgrade Jefferson Lab will measure pion and kaon form factors in this intermediate region, up to Q2 of 6 GeV2. This is then an ideal opportunity for lattice QCD to make an accurate prediction ahead of the experimental results. Lattice QCD provides a from-first-principles approach to calculate form factors, and the challenge here is to control the statistical and systematic uncertainties as errors grow when going to higher Q2 values. Here we report on a calculation that tests the method using an ηs meson, a 'heavy pion' made of strange quarks, and also present preliminary results for kaon and pion form factors. We use the nf = 2 + 1 + 1 ensembles made by the MILC collaboration and Highly Improved Staggered Quarks, which allows us to obtain high statistics. The HISQ action is also designed to have small dicretisation errors. Using several light quark masses and lattice spacings allows us to control the chiral and continuum extrapolation and keep systematic errors in check. Warning, no authors found for 2018EPJWC.17506016.
The IR sector of QCD: lattice versus Schwinger-Dyson equations
International Nuclear Information System (INIS)
Binosi, Daniele
2010-01-01
Important information about the infrared dynamics of QCD is encoded in the behavior of its (of-shell) Green's functions, most notably the gluon and the ghost propagators. Due to recent improvements in the quality of lattice data and the truncation schemes employed for the Schwinger-Dyson equations we have now reached a point where the interplay between these two non-perturbative tools can be most fruitful. In this talk several of the above points will be reviewed, with particular emphasis on the implications for the ghost sector, the non-perturbative effective charge of QCD, and the Kugo-Ojima function.
Lattice QCD computations: Recent progress with modern Krylov subspace methods
Energy Technology Data Exchange (ETDEWEB)
Frommer, A. [Bergische Universitaet GH Wuppertal (Germany)
1996-12-31
Quantum chromodynamics (QCD) is the fundamental theory of the strong interaction of matter. In order to compare the theory with results from experimental physics, the theory has to be reformulated as a discrete problem of lattice gauge theory using stochastic simulations. The computational challenge consists in solving several hundreds of very large linear systems with several right hand sides. A considerable part of the world`s supercomputer time is spent in such QCD calculations. This paper presents results on solving systems for the Wilson fermions. Recent progress is reviewed on algorithms obtained in cooperation with partners from theoretical physics.
Moments of nucleon generalized parton distributions from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Cyprus Institute, Nicosia; Carbonell, J.; Harraud, P.A.; Papinutto, M.; Constantinou, M.; Kallidonis, C.; Guichon, P.; Jansen, K.; Korzec, T.; Humboldt Univ. Berlin
2011-07-01
We present results on the lower moments of the nucleon generalized parton distributions within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Our simulations are performed on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined using simulations on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized nonperturbatively and the values are given in the MS scheme at a scale μ=2 GeV. They are chirally extrapolated to the physical point in order to compare with experiment. The consequences of these results on the spin carried by the quarks in the nucleon are investigated. (orig.)
Uses of Effective Field Theory in Lattice QCD
Kronfeld, Andreas S.
2002-01-01
Several physical problems in particle physics, nuclear physics, and astrophysics require information from non-perturbative QCD to gain a full understanding. In some cases the most reliable technique for quantitative results is to carry out large-scale numerical calculations in lattice gauge theory. As in any numerical technique, there are several sources of uncertainty. This chapter explains how effective field theories are used to keep them under control and, then, obtain a sensible error ba...
An analysis of the nucleon spectrum from lattice partially-quenched QCD
Energy Technology Data Exchange (ETDEWEB)
Armour, W. [Swansea University, Swansea, SA2 8PP, Wales, U.K.; Allton, C. R. [Swansea University, Swansea, SA2 8PP, Wales, U.K.; Leinweber, Derek B. [Univ. of Adelaide, SA (Australia); Thomas, Anthony W. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Young, Ross D. [Argonne National Lab. (ANL), Argonne, IL (United States)
2010-09-01
The chiral extrapolation of the nucleon mass, Mn, is investigated using data coming from 2-flavour partially-quenched lattice simulations. The leading one-loop corrections to the nucleon mass are derived for partially-quenched QCD. A large sample of lattice results from the CP-PACS Collaboration is analysed, with explicit corrections for finite lattice spacing artifacts. The extrapolation is studied using finite range regularised chiral perturbation theory. The analysis also provides a quantitative estimate of the leading finite volume corrections. It is found that the discretisation, finite-volume and partial quenching effects can all be very well described in this framework, producing an extrapolated value of Mn in agreement with experiment. This procedure is also compared with extrapolations based on polynomial forms, where the results are less encouraging.
$B$- and $D$-meson leptonic decay constants from four-flavor lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Bazavov, A. [Michigan State U.; Bernard, C. [Washington U., St. Louis; Brown, N. [Washington U., St. Louis; Detar, C. [Utah U.; El-Khadra, A. X. [Fermilab; Gámiz, E. [Granada U., Theor. Phys. Astrophys.; Gottlieb, Steven [Indiana U.; Heller, U. M. [APS, New York; Komijani, J. [TUM-IAS, Munich; Kronfeld, A. S. [TUM-IAS, Munich; Laiho, J. [Syracuse U.; Mackenzie, P. B. [Fermilab; Neil, E. T. [RIKEN BNL; Simone, J. N. [Fermilab; Sugar, R. L. [UC, Santa Barbara; Toussaint, D. [Glasgow U.; Van De Water, R. S. [Fermilab
2017-12-26
We calculate the leptonic decay constants of heavy-light pseudoscalar mesons with charm and bottom quarks in lattice quantum chromodynamics on four-flavor QCD gauge-field configurations with dynamical $u$, $d$, $s$, and $c$ quarks. We analyze over twenty isospin-symmetric ensembles with six lattice spacings down to $a\\approx 0.03$~fm and several values of the light-quark mass down to the physical value $\\frac{1}{2}(m_u+m_d)$. We employ the highly-improved staggered-quark (HISQ) action for the sea and valence quarks; on the finest lattice spacings, discretization errors are sufficiently small that we can calculate the $B$-meson decay constants with the HISQ action for the first time directly at the physical $b$-quark mass. We obtain the most precise determinations to-date of the $D$- and $B$-meson decay constants and their ratios, $f_{D^+} = 212.6 (0.5)$~MeV, $f_{D_s} = 249.8(0.4)$~MeV, $f_{D_s}/f_{D^+} = 1.1749(11)$, $f_{B^+} = 189.4(1.4)$~MeV, $f_{B_s} = 230.7(1.2)$~MeV, $f_{B_s}/f_{B^+} = 1.2180(49)$, where the errors include statistical and all systematic uncertainties. Our results for the $B$-meson decay constants are three times more precise than the previous best lattice-QCD calculations, and bring the QCD errors in the Standard-Model predictions for the rare leptonic decays $\\overline{\\mathcal{B}}(B_s \\to \\mu^+\\mu^-) = 3.65(11) \\times 10^{-9}$, $\\overline{\\mathcal{B}}(B^0 \\to \\mu^+\\mu^-) = 1.00(3) \\times 10^{-11}$, and $\\overline{\\mathcal{B}}(B^0 \\to \\mu^+\\mu^-)/\\overline{\\mathcal{B}}(B_s \\to \\mu^+\\mu^-) = 0.00264(7)$ to well below other sources of uncertainty. As a byproduct of our analysis, we also update our previously published results for the light-quark-mass ratios and the scale-setting quantities $f_{p4s}$, $M_{p4s}$, and $R_{p4s}$. We obtain the most precise lattice-QCD determination to date of the ratio $f_{K^+}/f_{\\pi^+} = 1.1950(^{+15}_{-22})$~MeV.
Algorithms for Disconnected Diagrams in Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gambhir, Arjun Singh [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Stathopoulos, Andreas [College of William and Mary, Williamsburg, VA (United States); Orginos, Konstantinos [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Yoon, Boram [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gupta, Rajan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Syritsyn, Sergey [Stony Brook Univ., NY (United States)
2016-11-01
Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm.
Electrical conductivity and charge diffusion in thermal QCD from the lattice
Energy Technology Data Exchange (ETDEWEB)
Aarts, Gert; Allton, Chris [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Amato, Alessandro [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Department of Physics and Helsinki Institute of Physics P.O. Box 64, FI-00014 University of Helsinki (Finland); Giudice, Pietro [Universität Münster, Institut für Theoretische Physik Wilhelm-Klemm-Str. 9, D-48149 Münster (Germany); Hands, Simon [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Skullerud, Jon-Ivar [Department of Mathematical Physics, National University of Ireland Maynooth Maynooth, Co Kildare (Ireland)
2015-02-27
We present a lattice QCD calculation of the charge diffusion coefficient, the electrical conductivity and various susceptibilities of conserved charges, for a range of temperatures below and above the deconfinement crossover. The calculations include the contributions from up, down and strange quarks. We find that the diffusion coefficient is of the order of 1/(2πT) and has a dip around the crossover temperature. Our results are obtained with lattice simulations containing 2+1 dynamical flavours on anisotropic lattices. The Maximum Entropy Method is used to construct spectral functions from correlators of the conserved vector current.
$N^*$ Resonances in Lattice QCD from (mostly) Low to (sometimes) High Virtualities
Energy Technology Data Exchange (ETDEWEB)
Richards, David G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-11-01
I present a survey of calculations of the excited $N^*$ spectrum in lattice QCD. I then describe recent advances aimed at extracting the momentum-dependent phase shifts from lattice calculations, notably in the meson sector, and the potential for their application to baryons. I conclude with a discussion of calculations of the electromagnetic transition form factors to excited nucleons, including calculations at high $Q^2$.
Heavy-heavy-light quark potential in SU(3) lattice QCD
International Nuclear Information System (INIS)
Yamamoto, Arata; Suganuma, Hideo; Iida, Hideaki
2008-01-01
We perform the first study for the heavy-heavy-light quark (QQq) potential in SU(3) quenched lattice QCD with the Coulomb gauge. The calculations are done with the standard gauge and O(a)-improved Wilson fermion action on the 16 4 lattice at β=6.0. We calculate the energy of QQq systems as the function of the distance R between the two heavy quarks, and find that the QQq potential is well described with a Coulomb plus linear potential form up to the intermediate distance R≤0.8 fm. Compared to the static three-quark case, the effective string tension between the heavy quarks is significantly reduced by the finite-mass valence quark effect. This reduction is considered to be a general property for baryons
Minkowski space pion model inspired by lattice QCD running quark mass
Energy Technology Data Exchange (ETDEWEB)
Mello, Clayton S. [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil); Melo, J.P.B.C. de [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo, SP (Brazil); Frederico, T., E-mail: tobias@ita.br [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil)
2017-03-10
The pion structure in Minkowski space is described in terms of an analytic model of the Bethe–Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe–Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward–Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.
Minkowski space pion model inspired by lattice QCD running quark mass
Directory of Open Access Journals (Sweden)
Clayton S. Mello
2017-03-01
Full Text Available The pion structure in Minkowski space is described in terms of an analytic model of the Bethe–Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe–Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward–Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.
International Nuclear Information System (INIS)
Kronfeld, Andreas
2005-01-01
Quantum chromodynamics (QCD) is the quantum field theory describing the strong interactions of quarks bound inside hadrons. It is marvelous theory, which works (mathematically) at all distance scales. Indeed, for thirty years, theorists have known how to calculate short-distance properties of QCD, thanks to the (Nobel-worthy) idea of asymptotic freedom. More recently, numerical techniques applied to the strong-coupling regime of QCD have enabled us to compute long-distance bound-state properties. In this colloquium, we review these achievements and show how the new-found methods of calculation will influence high-energy physics.
Particle states of lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Kapoyannis, A.S.; Panagiotou, A.D. [University of Athens, Nuclear and Particle Physics Section, Faculty of Physics, Athens (Greece)
2017-11-15
We determine the degeneracy factor and the average particle mass of particles that produce the lattice QCD pressure and specific entropy at zero baryon chemical potential. The number of states of the gluons and the quarks are found to converge above T = 230 MeV to almost constant values, close to the number of states of an ideal quark-gluon phase, while their assigned masses retain high values. The number of states and the average mass of a system containing quarks in interaction with gluons are found to decrease steeply with increase of temperature between T ∝ 150 and 160 MeV, a region contained within the region of the chiral transition. The minimum value of the number of states within this temperature interval indicates that the states are of hadronic nature. (orig.)
Repulsive baryonic interactions and lattice QCD observables at imaginary chemical potential
Directory of Open Access Journals (Sweden)
Volodymyr Vovchenko
2017-12-01
Full Text Available The first principle lattice QCD methods allow to calculate the thermodynamic observables at finite temperature and imaginary chemical potential. These can be compared to the predictions of various phenomenological models. We argue that Fourier coefficients with respect to imaginary baryochemical potential are sensitive to modeling of baryonic interactions. As a first application of this sensitivity, we consider the hadron resonance gas (HRG model with repulsive baryonic interactions, which are modeled by means of the excluded volume correction. The Fourier coefficients of the imaginary part of the net-baryon density at imaginary baryochemical potential â corresponding to the fugacity or virial expansion at real chemical potential â are calculated within this model, and compared with the Nt=12 lattice data. The lattice QCD behavior of the first four Fourier coefficients up to Tâ185Â MeV is described fairly well by an interacting HRG with a single baryonâbaryon eigenvolume interaction parameter bâ1Â fm3, while the available lattice data on the difference Ï2BâÏ4B of baryon number susceptibilities is reproduced up to Tâ175Â MeV. Keywords: Hadron resonance gas, Excluded volume, Imaginary chemical potential
Baryon interactions from lattice QCD with physical quark masses - Nuclear forces and ΞΞ forces -
Doi, Takumi; Iritani, Takumi; Aoki, Sinya; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Miyamoto, Takaya; Nemura, Hidekatsu; Sasaki, Kenji
2018-03-01
We present the latest lattice QCD results for baryon interactions obtained at nearly physical quark masses. Nf = 2 + 1 nonperturbatively O(a)-improved Wilson quark action with stout smearing and Iwasaki gauge action are employed on the lattice of (96a)4 ≃(8.1fm)4 with a-1 ≃2.3 GeV, where mπ ≃146 MeV and mK ≃525 MeV. In this report, we study the two-nucleon systems and two-Ξ systems in 1S0 channel and 3S1-3D1 coupled channel, and extract central and tensor interactions by the HAL QCD method. We also present the results for the NΩ interaction in 5S2 channel which is relevant to the NΩ pair-momentum correlation in heavy-ion collision experiments.
Exponential noise reduction in Lattice QCD: new tools for new physics
CERN. Geneva
2017-01-01
The numerical computations of many quantities of theoretical and phenomenological interest are plagued by statistical errors which increase exponentially with the distance of the sources in the relevant correlators. Notable examples are baryon masses and matrix elements, the hadronic vacuum polarization and the light-by-light scattering contributions to the muon g-2, and the form factors of semileptonic B decays. Reliable and precise determinations of these quantities are very difficult if not impractical with state-of-the-art standard Monte Carlo integration schemes. I will discuss a recent proposal for factorizing the fermion determinant in lattice QCD that leads to a local action in the gauge field and in the auxiliary boson fields. Once combined with the corresponding factorization of the quark propagator, it paves the way for multi-level Monte Carlo integration in the presence of fermions opening new perspectives in lattice QCD and in its capability to unveil new physics. Exploratory results on the impac...
Mass spectrum of 1-+ exotic mesons from lattice QCD
International Nuclear Information System (INIS)
Cook, M. S.; Fiebig, H. R.
2006-01-01
Time correlation functions of a hybrid exotic meson operator, with J PC =1 -+ , generated in quenched lattice QCD are subjected to a (Bayesian) maximum entropy analysis. Five distinct spectral levels are uncovered. Their extrapolation into the physical pion mass region suggests a possible relationship to experimentally known states π 1 (1400) and π 1 (1600), and also to a state in the 2 GeV region carrying the same quantum numbers
Unified chiral analysis of the vector meson spectrum from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Wes Armour; Chris Allton; Derek Leinweber; Anthony Thomas; Ross Young
2005-10-13
The chiral extrapolation of the vector meson mass calculated in partially-quenched lattice simulations is investigated. The leading one-loop corrections to the vector meson mass are derived for partially-quenched QCD. A large sample of lattice results from the CP-PACS Collaboration is analysed, with explicit corrections for finite lattice spacing artifacts. To incorporate the effect of the opening decay channel as the chiral limit is approached, the extrapolation is studied using a necessary phenomenological extension of chiral effective field theory. This chiral analysis also provides a quantitative estimate of the leading finite volume corrections. It is found that the discretisation, finite-volume and partial quenching effects can all be very well described in this framework, producing an extrapolated value of $M_\\rho$ in excellent agreement with experiment. This procedure is also compared with extrapolations based on polynomial forms, where the results are much less enlightening.
SU(2)-breaking effects for meson masses in lattice QCD
International Nuclear Information System (INIS)
Bramon, A.; Casulleras, J.
1989-01-01
The quenched approximation of lattice QCD for Wilson fermions is used to calculate isospin breaking effects in the pseudoscalar- and vector-meson nonets. Mass differences inside the K and K * isodoublets and mixing phenomena for π 0 -η and ρ-ω are found to agree with the experimental data. A new and specific method of analysis is proposed and successfully tested. (orig.)
Aspects of confinement in QCD from lattice simulations
International Nuclear Information System (INIS)
Spielmann, Daniel
2011-01-01
We study confinement in quantum chromodynamics via numerical simulations in the framework of lattice gauge theory. In Landau gauge, the mechanism of confinement is related to the infrared behavior of the ghost and gluon propagators via the Gribov-Zwanziger and Kugo- Ojima scenarios. These scenarios entail a scaling behavior. Functional methods in the continuum allow both for this behavior and for decoupling solutions, while lattice simulations in three and four dimensions yield only the latter. A possible explanation for this mismatch is based on limitations of standard lattice gauge fixing methods. Hence, we investigate a number of alternative gauge fixing algorithms in pure SU(2) gauge theory in two, three and four dimensions. We find that stochastic quantization yields an infrared behavior of the propagators in agreement with the results of standard procedures, even though the Faddeev-Popov operator spectrum indicates some different properties. In the strong-coupling limit, our results challenge the standard picture. In particular, we find in a non-perturbative completion of Landau gauge an enormous effect of the Gribov ambiguity. It entails that no subset of infrared solutions can be excluded yet. Moreover, we study the gluon propagator with free boundary conditions. On large lattices, the results mostly show the standard behavior. We also examine non-periodic gauge transformations. Furthermore, we analyze two topics related to the phase diagram of QCD. First, we explore the sign problem for fermions on the lattice by simulating the three-dimensional Thirring model with a complex Langevin equation. The algorithm succeeds in yielding a 'Silver Blaze' behavior of observables, but it does not reliably describe the onset to a phase with non-zero density. Second, we determine properties of the deconfinement phase transition of pure SU(2) gauge theory in 2+1 dimensions, like the critical temperature, by means of the gluon propagator in Landau gauge. (orig.)
Aspects of confinement in QCD from lattice simulations
Energy Technology Data Exchange (ETDEWEB)
Spielmann, Daniel
2011-01-12
We study confinement in quantum chromodynamics via numerical simulations in the framework of lattice gauge theory. In Landau gauge, the mechanism of confinement is related to the infrared behavior of the ghost and gluon propagators via the Gribov-Zwanziger and Kugo- Ojima scenarios. These scenarios entail a scaling behavior. Functional methods in the continuum allow both for this behavior and for decoupling solutions, while lattice simulations in three and four dimensions yield only the latter. A possible explanation for this mismatch is based on limitations of standard lattice gauge fixing methods. Hence, we investigate a number of alternative gauge fixing algorithms in pure SU(2) gauge theory in two, three and four dimensions. We find that stochastic quantization yields an infrared behavior of the propagators in agreement with the results of standard procedures, even though the Faddeev-Popov operator spectrum indicates some different properties. In the strong-coupling limit, our results challenge the standard picture. In particular, we find in a non-perturbative completion of Landau gauge an enormous effect of the Gribov ambiguity. It entails that no subset of infrared solutions can be excluded yet. Moreover, we study the gluon propagator with free boundary conditions. On large lattices, the results mostly show the standard behavior. We also examine non-periodic gauge transformations. Furthermore, we analyze two topics related to the phase diagram of QCD. First, we explore the sign problem for fermions on the lattice by simulating the three-dimensional Thirring model with a complex Langevin equation. The algorithm succeeds in yielding a 'Silver Blaze' behavior of observables, but it does not reliably describe the onset to a phase with non-zero density. Second, we determine properties of the deconfinement phase transition of pure SU(2) gauge theory in 2+1 dimensions, like the critical temperature, by means of the gluon propagator in Landau gauge. (orig.)
Pseudoscalar decay constants from Nf=2+1+1 twisted mass lattice QCD
International Nuclear Information System (INIS)
Farchioni, Federico; Petschlies, Marcus; Urbach, Carsten
2010-12-01
We present first results for the pseudoscalar decay constants f K , f D and f D S from lattice QCD with N f = 2 + 1 + 1 flavours of dynamical quarks. The lattice simulations have been performed by the European Twisted Mass collaboration (ETMC) using maximally twisted mass quarks. For the pseudoscalar decay constants we follow a mixed action approach by using so called Osterwalder-Seiler fermions in the valence sector for strange and charm quarks. The data for two values of the lattice spacing and several values of the up/down quark mass is analysed using chiral perturbation theory. (orig.)
Analytic determination at one loop of the energy-momentum tensor for lattice QCD
International Nuclear Information System (INIS)
Caracciolo, S.; Menotti, P.; Pelissetto, A.
1991-01-01
We give a completely analytical determinaton of the corrections to the naive energy-momentum tensor for lattice QCD at one loop. This tenor is conserved and gives rise to the correct trace anomaly. (orig.)
ChPT calculations for the analysis of lattice QCD data
International Nuclear Information System (INIS)
Greil, Ludwig
2014-01-01
We present calculations within the framework of three-flavor chiral perturbation theory (ChPT) for several observables (first moments of parton distributions, baryon octet masses and vector meson masses including phi-omega-mixing). We use lattice QCD data to determine the local couplings appearing in this chosen effective theory and we use these extrapolations to study the convergence of the chiral expansion around the symmetric point where all light quark masses have the same value. We also comment on the various benefits that stem from an expansion around the symmetric point.
Large N lattice QCD and its extended strong-weak connection to the hypersphere
International Nuclear Information System (INIS)
Christensen, Alexander S.; Myers, Joyce C.; Pedersen, Peter D.
2014-01-01
We calculate an effective Polyakov line action of QCD at large N c and large N f from a combined lattice strong coupling and hopping expansion working to second order in both, where the order is defined by the number of windings in the Polyakov line. We compare with the action, truncated at the same order, of continuum QCD on S 1 ×S d at weak coupling from one loop perturbation theory, and find that a large N c correspondence of equations of motion found in http://dx.doi.org/10.1007/JHEP10(2012)067 at leading order, can be extended to the next order. Throughout the paper, we review the background necessary for computing higher order corrections to the lattice effective action, in order to make higher order comparisons more straightforward
Hadron electric polarizability from lattice QCD
Alexandru, Andrei
2017-09-01
Electromagnetic polarizabilities are important parameters for hadron structure, describing the response of the charge and current distributions inside the hadron to an external electromagnetic field. For most hadrons these quantities are poorly constrained experimentally since they can only be measured indirectly. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the neutron electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies. For each pion mass we compute the polarizability at four different volumes and perform an infinite volume extrapolation. We also discuss the effect of turning on the coupling between the background field and the sea quarks. A.A. is supported in part by the National Science Foundation CAREER Grant PHY-1151648 and by U.S. DOE Grant No. DE-FG02-95ER40907.
Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Palombi, F. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Papinutto, M.; Pena, C. [CERN, Geneva (Switzerland). Physics Dept., Theory Div.; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik
2007-06-15
We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of {delta}B=2 parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by nonperturbatively O(a) improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered. (orig.)
Energy Technology Data Exchange (ETDEWEB)
BLUM, T.; BOER, D.; CREUTZ, M.; OHTA, S.; ORGINOS, K.
2002-03-18
The RIKEN BNL Research Center workshop on ''Hadron Structure from Lattice QCD'' was held at BNL during March 11-15, 2002. Hadron structure has been the subject of many theoretical and experimental investigations, with significant success in understanding the building blocks of matter. The nonperturbative nature of QCD, however, has always been an obstacle to deepening our understanding of hadronic physics. Lattice QCD provides the tool to overcome these difficulties and hence a link can be established between the fundamental theory of QCD and hadron phenomenology. Due to the steady progress in improving lattice calculations over the years, comparison with experimentally measured hadronic quantities has become important. In this respect the workshop was especially timely. By providing an opportunity for experts from the lattice and hadron structure communities to present their latest results, the workshop enhanced the exchange of knowledge and ideas. With a total of 32 registered participants and 26 talks, the interest of a growing community is clearly exemplified. At the workshop Schierholz and Negele presented the current status of lattice computations of hadron structure. Substantial progress has been made during recent years now that the quenched results are well under control and the first dynamical results have appeared. In both the dynamical and the quenched simulations the lattice results, extrapolated to lighter quark masses, seem to disagree with experiment. Melnitchouk presented a possible explanation (chiral logs) for this disagreement. It became clear from these discussions that lattice computations at significantly lighter quark masses need to be performed.
Leading-order hadronic contribution to g-2 from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Renner, Dru B.; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Feng, Xu [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Petschlies, Marcus [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik
2011-03-15
We calculate the leading-order hadronic correction to the anomalous magnetic moments of each of the three charged leptons in the Standard Model: the electron, muon and tau. Working in two-flavor lattice QCD, we address essentially all sources of systematic error: lattice artifacts, finite-size effects, quark-mass extrapolation, momentum extrapolation and disconnected diagrams. The most significant remaining systematic error, the exclusion of the strange and charm quark contributions, is addressed in our four-flavor calculation. We achieve a statistical accuracy of 2% or better for the physical values for each of the three leptons and the systematic errors are at most comparable. (orig.)
Non-perturbative O(a) improvement of lattice QCD
Lüscher, Martin; Sommer, Rainer; Weisz, P; Wolff, U; Luescher, Martin; Sint, Stefan; Sommer, Rainer; Weisz, Peter; Wolff, Ulli
1997-01-01
The coefficients multiplying the counterterms required for O($a$) improvement of the action and the isovector axial current in lattice QCD are computed non-perturbatively, in the quenched approximation and for bare gauge couplings $g_0$ in the range $0 \\leq g_0 \\leq 1$. A finite-size method based on the Schrödinger functional is employed, which enables us to perform all calculations at zero or nearly zero quark mass. As a by-product the critical hopping parameter $\\kappa_c$ is obtained at all couplings considered.
Hadron spectrum in quenched lattice QCD and quark potential models
International Nuclear Information System (INIS)
Iwasaki, Y.; Yoshie, T.
1989-01-01
We show that the quenched lattice QCD gives a hadron spectrum which remarkably agrees with that of quark potential models for quark mass m q ≥ m strange , even when one uses the standard one-plaquette gauge action. This is contrary to what is stated in the literature. We clarify the reason of the discrepancy, paying close attention to systematic errors in numerical calculations. (orig.)
Induced Chern-Simons term in lattice QCD at finite temperature
International Nuclear Information System (INIS)
Borisenko, O.A.; Petrov, V.K.; Zinovjev, G.M.
1995-01-01
The general conditions for the Chern-Simons action to be induced as a non-universal contribution of fermionic determinant are formulated in finite-temperature lattice QCD. The dependence of the corresponding coefficient in the action on non-universal parameters (chemical potentials, vacuum features, etc.) is explored. Special attention is paid to the role of A 0 -condensate if it is available in this theory. ((orig.))
Moment analysis of hadronic vacuum polarization. Proposal for a lattice QCD evaluation of gμ - 2
de Rafael, Eduardo
2014-09-01
I suggest a new approach to the determination of the hadronic vacuum polarization (HVP) contribution to the anomalous magnetic moment of the muon aμHVP in lattice QCD. It is based on properties of the Mellin transform of the hadronic spectral function and their relation to the HVP self-energy in the Euclidean. I show how aμHVP is very well approximated by a few moments associated to this Mellin transform and how these moments can be evaluated in lattice QCD, providing thus a series of tests when compared with the corresponding determinations using experimental data.
Effects of LatticeQCD EoS and Continuous Emission on Some Observables
International Nuclear Information System (INIS)
Hama, Y.; Andrade, R.; Grassi, F.; Socolowski, O.; Kodama, T.; Tavares, B.; Padula, S. S.
2006-01-01
Effects of lattice-QCD-inspired equations of state and continuous emission on some observables are discussed, by solving a 3D hydrodynamics. The particle multiplicity as well ν 2 are found to increase in the mid-rapidity. We also discuss the effects of the initial-condition fluctuations
Overlap between Lattice QCD and HRG with in-medium effects and parity doubling*
Directory of Open Access Journals (Sweden)
Morita Kenji
2018-01-01
Full Text Available We investigate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Temperature-dependent masses are adopted from the recent lattice QCD results and from a chiral effective model which implements the parity doubling structure with respect to the chiral symmetry. Confronting the baryon number susceptibility, baryon-charge correlation, and baryon-strangeness correlation and their ratios with the lattice QCD data, we show that the strong downward mass shift in hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations. This indicates, that in order to correctly account for the influence of the chiral symmetry restoration on the fluctuation observables, a consistent framework of in-medium effects beyond hadron mass shifts is required.
Lattice Studies of Hyperon Spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Richards, David G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-04-01
I describe recent progress at studying the spectrum of hadrons containing the strange quark through lattice QCD calculations. I emphasise in particular the richness of the spectrum revealed by lattice studies, with a spectrum of states at least as rich as that of the quark model. I conclude by prospects for future calculations, including in particular the determination of the decay amplitudes for the excited states.
Lattice QCD evaluation of baryon magnetic moment sum rules
International Nuclear Information System (INIS)
Leinweber, D.B.
1991-05-01
Magnetic moment combinations and sum rules are evaluated using recent results for the magnetic moments of octet baryons determined in a numerical simulation of quenched QCD. The model-independent and parameter-free results of the lattice calculations remove some of the confusion and contradiction surrounding past magnetic moment sum rule analyses. The lattice results reveal the underlying quark dynamics investigated by magnetic moment sum rules and indicate the origin of magnetic moment quenching for the non-strange quarks in Σ. In contrast to previous sum rule analyses, the magnetic moments of nonstrange quarks in Ξ are seen to be enhanced in the lattice results. In most cases, the spin-dependent dynamics and center-of-mass effects giving rise to baryon dependence of the quark moments are seen to be sufficient to violate the sum rules in agreement with experimental measurements. In turn, the sum rules are used to further examine the results of the lattice simulation. The Sachs sum rule suggests that quark loop contributions not included in present lattice calculations may play a key role in removing the discrepancies between lattice and experimental ratios of magnetic moments. This is supported by other sum rules sensitive to quark loop contributions. A measure of the isospin symmetry breaking in the effective quark moments due to quark loop contributions is in agreement with model expectations. (Author) 16 refs., 2 figs., 2 tabs
Lattice QCD and physics beyond the Standar Model: an experimentalist perspective
Artuso, Marina
2017-01-01
The new frontier in elementary particle physics is to find evidence for new physics that may lead to a deeper understanding of observations such as the baryon-antibaryon asymmetry of the universe, mass hierarchy, dark matter, or dark energy to name a few. Flavor physics provides a wealth of opportunities to find such signatures, and a vast body of data taken at e+e- b-factories and at hadron machines has provided valuable information, and a few tantalizing ``tensions'' with respect to the Standard Model predictions. While the window for new physics is still open, the chance that its manifestations will be subtle is very real. A vibrant experimental program is ongoing, and significant upgrades, such as the upgraded LHCb experiment at LHC and Belle 2 at KEKb, are imminent. One of the challenges in extracting new physics from flavor physics data is the need to relate observed hadron decays to fundamental particles and interactions. The continuous improvement of Lattice QCD predictions is a key element to achieve success in this quest. Improvements in algorithms and hardware have led to predictions of increasing precision on several fundamental matrix elements, and the continuous breaking of new grounds, thus allowing a broader spectrum of measurements to become relevant to this quest. An important aspect of the experiment-lattice synergy is a comparison between lattice predictions with experiment for a variety of hadronic quantities. This talk summarizes current synergies between lattice QCD theory and flavor physics experiments, and gives some highlights of expectations from future upgrades. this work was supported by NSF.
International Nuclear Information System (INIS)
Doi, Takumi
2013-01-01
Research of nuclear forces by lattice QCD including inter-hadron interactions is presented. Determination of nuclear forces based on the first principle of QCD means to give underpinning of nuclear physics from the elementary particle standard model. Determining the unknown interactions such as hyperon forces or three-body ones gives large impacts not only to the nuclear physics but also to the universe or astrophysics. In this paper, the most up-to-date achievements as well as the scientific visions of future by using K computer is introduced. The nuclear potential is shown to be determined by the first principle simulation based on the purely fundamental theory without using any input from experiments. When this research is completed, nuclear physics is consolidated in the frame of standard model of elementary particles. The formulation of nuclear potentials was though very problematic but solved by using HAL method. The way to use Nambu-Bethe-Salpeter wave functions to go to the QCD is explained. The results of the lattice QCD simulation are shown about the nuclear force potential of 1 S 0 channel and the scattering phase differences. About the hyperon forces, computer results from the limit of flavor SU(3) where the masses of u, d and s quarks are equal are introduced here. Further studies using different quark masses are necessary and calculation taking the SU(3) breaking into consideration is in progress. The calculation result of triple proton channel is shown as an example of three-body forth, which is another important nuclear force. To let the lattice QCD exert the predicting ability further steps are left. Calculations on real quark masses are considered especially important as the future problem. Confronting the large problem of hadron many-body systems, K computer is the biggest challenging force as well as the new formalism of HAL QCD and Unified Contraction Algorithm (UCA). (S. Funahashi)
Overlap valence quarks on a twisted mass sea. A case study for mixed action lattice QCD
International Nuclear Information System (INIS)
Cichy, Krzysztof; Herdoiza, Gregorio; UAM/CSIC Univ. Autonoma de Madrid
2012-11-01
We discuss a Lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like locality in the continuum limit. We also show that by adopting suitable matching conditions for the sea and valence theories a consistent continuum limit for the pion decay constant and light baryon masses can be obtained. Finally, we confront results for sea-valence mixed meson masses and the valence scalar correlator with corresponding expressions of chiral perturbation theory. This allows us to extract low energy constants of mixed action chiral perturbation which characterize the strength of unitarity violations in our mixed action setup.
Overlap valence quarks on a twisted mass sea. A case study for mixed action lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Drach, Vincent; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Garcia-Ramos, Elena [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany); Herdoiza, Gregorio [UAM/CSIC Univ. Autonoma de Madrid (Spain). Dept. de Fisica Teorica; UAM/CSIC Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica; Collaboration: European Twisted Mass Collaboration
2012-11-15
We discuss a Lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like locality in the continuum limit. We also show that by adopting suitable matching conditions for the sea and valence theories a consistent continuum limit for the pion decay constant and light baryon masses can be obtained. Finally, we confront results for sea-valence mixed meson masses and the valence scalar correlator with corresponding expressions of chiral perturbation theory. This allows us to extract low energy constants of mixed action chiral perturbation which characterize the strength of unitarity violations in our mixed action setup.
Thermodynamics of lattice QCD with 2 quark flavours : chiral symmetry and topology
International Nuclear Information System (INIS)
Lagae, J.-F.
1998-01-01
We have studied the restoration of chiral symmetry in lattice QCD at the finite temperature transition from hadronic matter to a quark-gluon plasma. By measuring the screening masses of flavour singlet and non-singlet meson excitations, we have seen evidence that, although flavour chiral symmetry is restored at this transition, flavour singlet (U(1)) axial symmetry is not. We conclude that this indicates that instantons continue to play an important role in the quark-gluon plasma phase
Non-perturbative chiral corrections for lattice QCD
International Nuclear Information System (INIS)
Thomas, A.W.; Leinweber, D.B.; Lu, D.H.
2002-01-01
We explore the chiral aspects of extrapolation of observables calculated within lattice QCD, using the nucleon magnetic moments as an example. Our analysis shows that the biggest effects of chiral dynamics occur for quark masses corresponding to a pion mass below 600 MeV. In this limited range chiral perturbation theory is not rapidly convergent, but we can develop some understanding of the behaviour through chiral quark models. This model dependent analysis leads us to a simple Pade approximant which builds in both the limits m π → 0 and m π → ∞ correctly and permits a consistent, model independent extrapolation to the physical pion mass which should be extremely reliable. (author)
Charm quark mass and D-meson decay constants from two-flavour lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Heitger, Jochen [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Hippel, Georg M. von [Mainz Univ. (Germany). Inst. fuer Kernphysik; Schaefer, Stefan; Virotta, Francesco [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2013-12-15
We present a computation of the charm quark's mass and the leptonic D-meson decay constants f{sub D} and f{sub D{sub s}} in two-flavour lattice QCD with non-perturbatively O(a) improvedWilson quarks. Our analysis is based on the CLS configurations at two lattice spacings (a=0.065 and 0.048 fm, where the lattice scale is set by f{sub K}) and pion masses ranging down to {proportional_to}190 MeV at Lm{sub {pi}}>or similar 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties.
The {pi}{sup +}{pi}{sup +} scattering length from maximally twisted mass lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Feng, Xu [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Jansen, Karl; Renner, Dru [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2009-12-15
We calculate the s-wave pion-pion scattering length in the isospin I=2 channel in lattice QCD for pion masses ranging from 270 Mev to 485 Mev using two flavors of maximally twisted mass fermions at a lattice spacing of 0.086 fm. Additionally, we check for lattice artifacts with one calculation at a finer lattice spacing of 0.067 fm. We use chiral perturbation theory at next-to-leading order to extrapolate our results. At the physical pion mass, we find m{sub {pi}}a{sup I=2}{sub {pi}}{sub {pi}}=-0.04385(28)(38) for the scattering length, where the first error is statistical and the second is our estimate of several systematic effects. (orig.)
ΛcN interaction from lattice QCD and its application to Λc hypernuclei
Miyamoto, Takaya; Aoki, Sinya; Doi, Takumi; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Kawai, Daisuke; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji
2018-03-01
The interaction between Λc and a nucleon (N) is investigated by employing the HAL QCD method in the (2 + 1)-flavor lattice QCD on a (2.9fm) 3 volume at mπ ≃ 410 , 570 , 700 MeV. We study the central potential in S10 channel as well as central and tensor potentials in S31-3D1 channel, and find that the tensor potential for Λc N is negligibly weak and central potentials in both S10 and S31-3D1 channels are almost identical with each other except at short distances. Phase shifts and scattering lengths calculated with these potentials show that the interaction of Λc N system is attractive and has a similar strength in S10 and S31 channels at low energies (i.e. the kinetic energy less than about 40 MeV). While the attractions are not strong enough to form two-body bound states, our results lead to a possibility to form Λc hypernuclei for sufficiently large atomic numbers (A). To demonstrate this, we derive a single-folding potential for Λc hypernuclei from the Λc-nucleon potential obtained in lattice QCD, and find that Λc hypernuclei can exist for A ≥ 12 with the binding energies of a few MeV. We also estimate the Coulomb effect for the Λc hypernuclei.
Valence QCD: Connecting QCD to the quark model
International Nuclear Information System (INIS)
Liu, K.F.; Dong, S.J.; Draper, T.; Sloan, J.; Leinweber, D.; Woloshyn, R.M.
1999-01-01
A valence QCD theory is developed to study the valence quark properties of hadrons. To keep only the valence degrees of freedom, the pair creation through the Z graphs is deleted in the connected insertions, whereas the sea quarks are eliminated in the disconnected insertions. This is achieved with a new 'valence QCD' Lagrangian where the action in the time direction is modified so that the particle and antiparticle decouple. It is shown in this valence version of QCD that the ratios of isovector to isoscalar matrix elements (e.g., F A /D A and F S /D S ratios) in the nucleon reproduce the SU(6) quark model predictions in a lattice QCD calculation. We also consider how the hadron masses are affected on the lattice and discover new insights into the origin of dynamical mass generation. It is found that, within statistical errors, the nucleon and the Δ become degenerate for the quark masses we have studied (ranging from 1 to 4 times the strange mass). The π and ρ become nearly degenerate in this range. It is shown that valence QCD has the C, P, T symmetries. The lattice version is reflection positive. It also has the vector and axial symmetries. The latter leads to a modified partially conserved axial Ward identity. As a result, the theory has a U(2N F ) symmetry in the particle-antiparticle space. Through lattice simulation, it appears that this is dynamically broken down to U q (N F )xU bar q (N F ). Furthermore, the lattice simulation reveals spin degeneracy in the hadron masses and various matrix elements. This leads to an approximate U q (2N F )xU bar q (2N F ) symmetry which is the basis for the valence quark model. In addition, we find that the masses of N, Δ,ρ,π,a 1 , and a 0 all drop precipitously compared to their counterparts in the quenched QCD calculation. This is interpreted as due to the disappearance of the 'constituent' quark mass which is dynamically generated through tadpole diagrams. The origin of the hyperfine splitting in the baryon is
Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Meyer, Aaron S. [Fermilab; Hill, Richard J. [Perimeter Inst. Theor. Phys.; Kronfeld, Andreas S. [Fermilab; Li, Ruizi [Indiana U.; Simone, James N. [Fermilab
2016-10-14
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
Partially quenched lattice QCD with two degenerate dynamical light Wilson quarks
International Nuclear Information System (INIS)
De, Asit K.; Harindranath, A.; Maiti, Jyotirmoy
2006-01-01
We present our results of numerical studies of partially quenched latticed QCD with two degenerate flavors of dynamical quarks. Gauge configurations are generated with Wilson gauge action and tadpole improved Wilson fermions at β = 5.6 and K sea = 0.155, 0.156, 0.157 and 0.158. Suitably smeared gauge configurations are used to calculate the static interquark potential in order to set the physical scale. Mesonic propagators are calculated at above mentioned four different values of K val for each K sea . We present results for pion and rho masses. (author)
International Nuclear Information System (INIS)
Fiebig, H. Rudolf
2002-01-01
We study various aspects of extracting spectral information from time correlation functions of lattice QCD by means of Bayesian inference with an entropic prior, the maximum entropy method (MEM). Correlator functions of a heavy-light meson-meson system serve as a repository for lattice data with diverse statistical quality. Attention is given to spectral mass density functions, inferred from the data, and their dependence on the parameters of the MEM. We propose to employ simulated annealing, or cooling, to solve the Bayesian inference problem, and discuss the practical issues of the approach
Light hadrons from lattice QCD with light (u,d), strange and charm dynamical quarks
International Nuclear Information System (INIS)
Baron, R.
2010-04-01
We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (N f =2+1+1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark masses is performed at two values of the lattice spacing a ∼ 0:078 fm and a ∼0.086 fm with lattice sizes ranging from L∼1.9 fm to L∼2.8 fm. We measure with high statistical precision the light pseudoscalar mass m PS and decay constant f PS in a range 270 PS 0 and anti l 3,4 of SU(2) chiral perturbation theory. We use the two values of the lattice spacing, several lattice sizes as well as different values of the light, strange and charm quark masses to explore the systematic effects. A first study of discretisation effects in light-quark observables and a comparison to N f =2 results are performed. (orig.)
Chakraborty, B.; Davies, C. T. H.; Detar, C.; El-Khadra, A. X.; Gámiz, E.; Gottlieb, Steven; Hatton, D.; Koponen, J.; Kronfeld, A. S.; Laiho, J.; Lepage, G. P.; Liu, Yuzhi; MacKenzie, P. B.; McNeile, C.; Neil, E. T.; Simone, J. N.; Sugar, R.; Toussaint, D.; van de Water, R. S.; Vaquero, A.; Fermilab Lattice, Hpqcd,; Milc Collaborations
2018-04-01
All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to aμHVP for the first time with physical values of mu and md and dynamical u , d , s , and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of δ aμHVP ,mu≠md=+1.5 (7 )% , in agreement with estimates from phenomenology.
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
International Nuclear Information System (INIS)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M.; Pleiter, D.; Stueben, H.
2014-03-01
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q 2 in the range 0.2-1.3 GeV 2 . The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μ p G E p /G M p . This quantity decreases with Q 2 in a way qualitatively consistent with recent experimental results.
Doubly magic nuclei from lattice QCD forces at MPS=469 MeV /c2
McIlroy, C.; Barbieri, C.; Inoue, T.; Doi, T.; Hatsuda, T.
2018-02-01
We perform ab initio self-consistent Green's function calculations of the closed shell nuclei 4He, 16O, and 40Ca, based on two-nucleon potentials derived from lattice QCD simulations, in the flavor SU(3) limit and at the pseudoscalar meson mass of 469 MeV/c2. The nucleon-nucleon interaction is obtained using the hadrons-to-atomic-nuclei-from-lattice (HAL) QCD method, and its short-distance repulsion is treated by means of ladder resummations outside the model space. Our results show that this approach diagonalizes ultraviolet degrees of freedom correctly. Therefore, ground-state energies can be obtained from infrared extrapolations even for the relatively hard potentials of HAL QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total binding energies are sensibly improved by the full account of many-body correlations. The results suggest an interesting possible behavior in which nuclei are unbound at very large pion masses and islands of stability appear at first around the traditional doubly magic numbers when the pion mass is lowered toward its physical value. The calculated one-nucleon spectral distributions are qualitatively close to those of real nuclei even for the pseudoscalar meson mass considered here.
Reducing cutoff effects in maximally twisted lattice QCD close to the chiral limit
International Nuclear Information System (INIS)
Frezzotti, R.; Papinutto, M.; Rossi, G.C.; Istituto Nazionale di Fisica Nucleare, Rome; Deutsches Elektronen-Synchrotron
2005-03-01
When analyzed in terms of the Symanzik expansion, the expectation values of multi-local (gauge-invariant) operators with non-trivial continuum limit exhibit in maximally twisted lattice QCD ''infrared divergent'' cutoff effects of the type a 2k /(m π 2 ) h , 2k ≥ h ≥ 1, which become numerically dangerous when the pion mass gets small. We prove that, if the critical mass counter-term is chosen in some ''optimal'' way or, alternatively, the action is O(a) improved a la Symanzik, the leading cutoff effects of this kind (i.e. those with h = 2k) can all be eliminated. Once this is done, the remaining next-to-leading ''infrared divergent'' effects are only of the kind a 2 (a 2 /m π 2 ) k , k ≥ 1. This implies that the continuum extrapolation of lattice results is smooth at least down to values of the quark mass, m q , satisfying the order of magnitude inequality m q > a 2 Λ QCD 3 . (orig.)
Hadronic correlation functions with quark-disconnected contributions in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Guelpers, Vera Magdalena
2015-09-14
One of the fundamental interactions in the Standard Model of particle physics is the strong force, which can be formulated as a non-abelian gauge theory called Quantum Chromodynamics (QCD). In the low-energy regime, where the QCD coupling becomes strong and quarks and gluons are confined to hadrons, a perturbative expansion in the coupling constant is not possible. However, the introduction of a four-dimensional Euclidean space-time lattice allows for an ab initio treatment of QCD and provides a powerful tool to study the low-energy dynamics of hadrons. Some hadronic matrix elements of interest receive contributions from diagrams including quark-disconnected loops, i.e. disconnected quark lines from one lattice point back to the same point. The calculation of such quark loops is computationally very demanding, because it requires knowledge of the all-to-all propagator. In this thesis we use stochastic sources and a hopping parameter expansion to estimate such propagators. We apply this technique to study two problems which relay crucially on the calculation of quark-disconnected diagrams, namely the scalar form factor of the pion and the hadronic vacuum polarization contribution to the anomalous magnet moment of the muon. The scalar form factor of the pion describes the coupling of a charged pion to a scalar particle. We calculate the connected and the disconnected contribution to the scalar form factor for three different momentum transfers. The scalar radius of the pion is extracted from the momentum dependence of the form factor. The use of several different pion masses and lattice spacings allows for an extrapolation to the physical point. The chiral extrapolation is done using chiral perturbation theory (χPT). We find that our pion mass dependence of the scalar radius is consistent with χPT at next-to-leading order. Additionally, we are able to extract the low energy constant anti l{sub 4} from the extrapolation, and our result is in agreement with results
Hadronic correlation functions with quark-disconnected contributions in lattice QCD
International Nuclear Information System (INIS)
Guelpers, Vera Magdalena
2015-01-01
One of the fundamental interactions in the Standard Model of particle physics is the strong force, which can be formulated as a non-abelian gauge theory called Quantum Chromodynamics (QCD). In the low-energy regime, where the QCD coupling becomes strong and quarks and gluons are confined to hadrons, a perturbative expansion in the coupling constant is not possible. However, the introduction of a four-dimensional Euclidean space-time lattice allows for an ab initio treatment of QCD and provides a powerful tool to study the low-energy dynamics of hadrons. Some hadronic matrix elements of interest receive contributions from diagrams including quark-disconnected loops, i.e. disconnected quark lines from one lattice point back to the same point. The calculation of such quark loops is computationally very demanding, because it requires knowledge of the all-to-all propagator. In this thesis we use stochastic sources and a hopping parameter expansion to estimate such propagators. We apply this technique to study two problems which relay crucially on the calculation of quark-disconnected diagrams, namely the scalar form factor of the pion and the hadronic vacuum polarization contribution to the anomalous magnet moment of the muon. The scalar form factor of the pion describes the coupling of a charged pion to a scalar particle. We calculate the connected and the disconnected contribution to the scalar form factor for three different momentum transfers. The scalar radius of the pion is extracted from the momentum dependence of the form factor. The use of several different pion masses and lattice spacings allows for an extrapolation to the physical point. The chiral extrapolation is done using chiral perturbation theory (χPT). We find that our pion mass dependence of the scalar radius is consistent with χPT at next-to-leading order. Additionally, we are able to extract the low energy constant anti l 4 from the extrapolation, and our result is in agreement with results from
Nucleon matrix elements using the variational method in lattice QCD
International Nuclear Information System (INIS)
Dragos, J.; Kamleh, W.; Leinweber, D.B.; Zanotti, J.M.; Rakow, P.E.L.; Young, R.D.; Adelaide Univ., SA
2016-06-01
The extraction of hadron matrix elements in lattice QCD using the standard two- and threepoint correlator functions demands careful attention to systematic uncertainties. One of the most commonly studied sources of systematic error is contamination from excited states. We apply the variational method to calculate the axial vector current g_A, the scalar current g_S and the quark momentum fraction left angle x right angle of the nucleon and we compare the results to the more commonly used summation and two-exponential fit methods. The results demonstrate that the variational approach offers a more efficient and robust method for the determination of nucleon matrix elements.
Properties of pseudoscalar flavour-singlet mesons from 2+1+1 twisted mass lattice QCD
International Nuclear Information System (INIS)
Cichy, Krzysztof; Poznan Univ.; Drach, Vincent; Garcia Ramos, Elena; Jansen, Karl; Michael, Chris; Ottnad, Konstantin; Urbach, Carsten; Zimmermann, Falk
2012-11-01
We study properties of pseudoscalar flavour-singlet mesons from Wilson twisted mass lattice QCD with N f =2+1+1 dynamical quark flavors. Results for masses are presented at three values of the lattice spacing and light quark masses corresponding to values of the pion mass from 230 MeV to 500 MeV. We briefly discuss scaling effects and the light and strange quark mass dependence of M η . In addition we present an exploratory study using Osterwalder-Seiler type strange and charm valence quarks. This approach avoids some of the complications of the twisted mass heavy doublet. We present first results for matching valence and unitary actions and a comparison of statistical uncertainties.
Properties of pseudoscalar flavour-singlet mesons from 2+1+1 twisted mass lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Drach, Vincent; Garcia Ramos, Elena; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Michael, Chris [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Ottnad, Konstantin; Urbach, Carsten; Zimmermann, Falk [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik
2012-11-15
We study properties of pseudoscalar flavour-singlet mesons from Wilson twisted mass lattice QCD with N{sub f}=2+1+1 dynamical quark flavors. Results for masses are presented at three values of the lattice spacing and light quark masses corresponding to values of the pion mass from 230 MeV to 500 MeV. We briefly discuss scaling effects and the light and strange quark mass dependence of M{sub {eta}}. In addition we present an exploratory study using Osterwalder-Seiler type strange and charm valence quarks. This approach avoids some of the complications of the twisted mass heavy doublet. We present first results for matching valence and unitary actions and a comparison of statistical uncertainties.
Simulation of N{sub f} = 2 + 1 lattice QCD at realistic quark masses
Energy Technology Data Exchange (ETDEWEB)
Schierholz, Gerrit
2014-07-01
So far most lattice QCD simulations are performed neglecting electromagnetic effects. In order to compute physical observables to high precision, it is important to include and control contributions from QED. We have initiated a similar program, as the symmetry of the electromagnetic current is similar to that of the mass matrix mass m=(m{sub u}+m{sub d}+m{sub s})/3=constant versus e{sub u}+e{sub d}+e{sub s}=constant=0. In a follow-up project we shall use this expansion and complement our previous simulations by a fully dynamical simulation of QCD+QED. (orig.)
Two-nucleon higher partial-wave scattering from lattice QCD
Directory of Open Access Journals (Sweden)
Evan Berkowitz
2017-02-01
Full Text Available We present a determination of nucleon-nucleon scattering phase shifts for ℓ≥0. The S, P, D and F phase shifts for both the spin-triplet and spin-singlet channels are computed with lattice Quantum ChromoDynamics. For ℓ>0, this is the first lattice QCD calculation using the Lüscher finite-volume formalism. This required the design and implementation of novel lattice methods involving displaced sources and momentum-space cubic sinks. To demonstrate the utility of our approach, the calculations were performed in the SU(3-flavor limit where the light quark masses have been tuned to the physical strange quark mass, corresponding to mπ=mK≈800 MeV. In this work, we have assumed that only the lowest partial waves contribute to each channel, ignoring the unphysical partial wave mixing that arises within the finite-volume formalism. This assumption is only valid for sufficiently low energies; we present evidence that it holds for our study using two different channels. Two spatial volumes of V≈(3.5 fm3 and V≈(4.6 fm3 were used. The finite-volume spectrum is extracted from the exponential falloff of the correlation functions. Said spectrum is mapped onto the infinite volume phase shifts using the generalization of the Lüscher formalism for two-nucleon systems.
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
Energy Technology Data Exchange (ETDEWEB)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M. [Adelaide Univ., SA (Australia). ARC Centre of Excellence in Particle Physics at the Terascale and CSSM; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe, Hyogo (Japan); Pleiter, D. [Forschungszentrum Juelich (Germany). JSC; Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Hamburg Univ. (Germany). Regionales Rechenzentrum; Collaboration: CSSM and QCDSF/UKQCD Collaborations
2014-03-15
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q{sup 2} in the range 0.2-1.3 GeV{sup 2}. The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μ{sub p}G{sub E}{sup p}/G{sub M}{sup p}. This quantity decreases with Q{sup 2} in a way qualitatively consistent with recent experimental results.
Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander
2016-01-01
We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched 323 × Nτ (β = 7.0, ξ = 3.5) lattices with Nτ = 24, …, 96, which cover 839MeV ≥ T ≥ 210MeV. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize Nf = 2 + 1 ASQTAD lattices with ml = ms/20 by the HotQCD collaboration, giving access to temperatures between 286MeV ≥ T ≥ 148MeV. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.
Color fields of the static pentaquark system computed in SU(3) lattice QCD
Cardoso, Nuno; Bicudo, Pedro
2013-02-01
We compute the color fields of SU(3) lattice QCD created by static pentaquark systems, in a 243×48 lattice at β=6.2 corresponding to a lattice spacing a=0.07261(85)fm. We find that the pentaquark color fields are well described by a multi-Y-type shaped flux tube. The flux tube junction points are compatible with Fermat-Steiner points minimizing the total flux tube length. We also compare the pentaquark flux tube profile with the diquark-diantiquark central flux tube profile in the tetraquark and the quark-antiquark fundamental flux tube profile in the meson, and they match, thus showing that the pentaquark flux tubes are composed of fundamental flux tubes.
Color fields computed in SU(3) lattice QCD for the static tetraquark system
International Nuclear Information System (INIS)
Cardoso, Nuno; Cardoso, Marco; Bicudo, Pedro
2011-01-01
The color fields created by the static tetraquark system are computed in quenched SU(3) lattice QCD, in a 24 3 x48 lattice at β=6.2 corresponding to a lattice spacing a=0.07261(85) fm. We find that the tetraquark color fields are well described by a double-Y, or butterfly, shaped flux tube. The two flux-tube junction points are compatible with Fermat points minimizing the total flux-tube length. We also compare the diquark-diantiquark central flux-tube profile in the tetraquark with the quark-antiquark fundamental flux-tube profile in the meson, and they match, thus showing that the tetraquark flux tubes are composed of fundamental flux tubes.
Why QCD lattice theory is important to spin physicists
International Nuclear Information System (INIS)
Rebbi, C.
1982-01-01
The lattice formulation of a quantum field theory allows calculations in the regime of strong coupling, by expansion techniques, and for intermediate coupling, by Monte Carlo simulations. These computations are especially valuable in the case of Quantum Chromodynamics (QCD), where several of the most important problems are not amenable to a perturbative analysis. Monte carlo simulations, in particular, have recently emerged as a very powerful tool and have been used to evaluate a variety of important physical quantities, such as the string tension, the deconfinement temperature, the scale of the interquark potential, glueball masses and masses in the quark model spectrum. If we consider those problems of strong interactions where spin plays an important role, it is unlikely, for the moment at least, that the lattice formulation may be of relevance where the phenomena being investigated involve propagations over extended domains of space-time; thus, for instance, it is impossible to perform a meaningful simulation of a scattering experiment on the lattice. But we are at the stage where Monte Carlo calculations begin to provide relevant information on spectroscopic properties related to spin. These are briefly discussed
Braun-Munzinger, P.; Redlich, K.; Stachel, J.
2016-01-01
We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge, strangeness and baryon number from experimental data on the particle production yields at midrapidity of the ALICE Collaboration at CERN. The data were taken in central Pb-Pb collisions at $\\sqrt{s_{\\rm NN}}$~=~2.76~TeV and cover one unit of rapidity. We show that the resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature $T_{c} \\simeq$ 155 MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. Since Lattice QCD calculations are performed at a baryochemical potential of $\\mu_{B}$ = 0, the comparisons with LHC data are the most direct due to the vanishing baryon transport to midrapidity at these high energies.
The chiral condensate from lattice QCD with Wilson twisted mass quarks
Energy Technology Data Exchange (ETDEWEB)
Urbach, Carsten [Bonn Univ. (Germany). HISKP (Theorie)
2016-11-01
Lattice QCD is a very computer time demanding scientific application. Only with the computer time made available on supercomputers like SuperMUC significant progress, like the one reported here, can be reached. Moreover, the computing resources made available by LRZ are used to reduce the systematic uncertainties in our results even further: in another project we are generating ensembles with physical values of the quark masses, such that a chiral extrapolation is not needed anymore.
Leading hadronic contributions to the running of the electroweak coupling constants from lattice QCD
International Nuclear Information System (INIS)
Burger, Florian; Jansen, Karl; Petschlies, Marcus; Pientka, Grit
2015-12-01
The quark-connected leading-order hadronic contributions to the running of the electromagnetic fine structure constant, α QED , and the weak mixing angle, θ W , are determined by a four-flavour lattice QCD computation with twisted mass fermions. Full agreement of the results with a phenomenological analysis is observed with an even comparable statistical uncertainty. We show that the uncertainty of the lattice calculation is dominated by systematic effects which then leads to significantly larger errors than obtained by the phenomenological analysis.
Axial-Current Matrix Elements in Light Nuclei from Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Savage, Martin [Univ. of Washington, Seattle, WA (United States); Shanahan, Phiala E. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Tiburzi, Brian C. [Univ. of Maryland, College Park, MD (United States); Wagman, Michael L. [Univ. of Washington, Seattle, WA (United States); Winter, Frank T. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Beane, Silas [Univ. of New Hampshire, Durham, NH (United States); Chang, Emmanuel [Univ. of Washington, Seattle, WA (United States); Davoudi, Zohreh; Detmold, William [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Orginos, Konstantinos [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)
2016-12-01
I present results from the first lattice QCD calculations of axial-current matrix elements in light nuclei, performed by the NPLQCD collaboration. Precision calculations of these matrix elements, and the subsequent extraction of multi-nucleon axial-current operators, are essential in refining theoretical predictions of the proton-proton fusion cross section, neutrino-nucleus cross sections and $\\beta\\beta$-decay rates of nuclei. In addition, they are expected to shed light on the phenomenological quenching of $g_A$ that is required in nuclear many-body calculations.
Lattice QCD with light quark masses: Does chiral symmetry get broken spontaneously
International Nuclear Information System (INIS)
Barbour, I.M.; Schierholz, G.; Teper, M.; Gilchrist, J.P.; Schneider, H.
1983-03-01
We present a first direct calculation of the properties of QCD for the small quark masses of phenomenological interest without extrapolations. We describe methods specially adapted to invert the fermion matrix at small quark masses. We use these methods to calculate directly on presently used lattice sizes with different boundary conditions. As is to be expected for a finite system, we do not observe spontaneous chiral symmetry breaking. By comparing the results obtained on lattices of different size we see, however, indications that are consistent with eventual spontaneous chiral symmetry breaking in the infinite volume limit. Our calculations underline the importance of using antiperiodic boundary conditions for fermions. (orig.)
ππ P-wave resonant scattering from lattice QCD
Directory of Open Access Journals (Sweden)
Paul Srijit
2018-01-01
Full Text Available We present a high-statistics analysis of the ρ resonance in ππ scattering, using 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV and a lattice size of approximately 3:6 fm. The computation of the two-point functions are carried out using combinations of forward, sequential, and stochastic propagators. For the extraction of the ρ-resonance parameters, we compare different fit methods and demonstrate their consistency. For the ππ scattering phase shift, we consider different Breit-Wigner parametrizations and also investigate possible nonresonant contributions. We find that the minimal Breit-Wigner model is suffcient to describe our data, and obtain amρ = 0:4609(16stat(14sys and gρππ = 5:69(13stat(16sys. In our comparison with other lattice QCD results, we consider the dimensionless ratios amρ/amN and amπ/amN to avoid scale setting ambiguities.
ππ P-wave resonant scattering from lattice QCD
Paul, Srijit; Alexandrou, Constantia; Leskovec, Luka; Meinel, Stefan; Negele, John W.; Petschlies, Marcus; Pochinsky, Andrew; Rendon Suzuki, Jesus Gumaro; Syritsyn, Sergey
2018-03-01
We present a high-statistics analysis of the ρ resonance in ππ scattering, using 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV and a lattice size of approximately 3:6 fm. The computation of the two-point functions are carried out using combinations of forward, sequential, and stochastic propagators. For the extraction of the ρ-resonance parameters, we compare different fit methods and demonstrate their consistency. For the ππ scattering phase shift, we consider different Breit-Wigner parametrizations and also investigate possible nonresonant contributions. We find that the minimal Breit-Wigner model is suffcient to describe our data, and obtain amρ = 0:4609(16)stat(14)sys and gρππ = 5:69(13)stat(16)sys. In our comparison with other lattice QCD results, we consider the dimensionless ratios amρ/amN and amπ/amN to avoid scale setting ambiguities.
Fermion determinants in lattice QCD
International Nuclear Information System (INIS)
Johnson, Christopher Andrew
2001-01-01
The main topic of this thesis concerns efficient algorithms for the calculation of determinants of the kind of matrix typically encountered in lattice QCD. In particular an efficient method for calculating the fermion determinant is described. Such a calculation is useful to illustrate the effects of light dynamical (virtual) quarks. The methods employed in this thesis are stochastic methods, based on the Lanczos algorithm, which is used for the solution of large, sparse matrix problems via a partial tridiagonalisation of the matrix. Here an implementation is explored which requires less exhaustive treatment of the matrix than previous Lanczos methods. This technique exploits the analogy between the Lanczos tridiagonalisation algorithm and Gaussian quadrature in order to calculate the fermion determinant. A technique for determining a number of the eigenvalues of the matrix is also presented. A demonstration is then given of how one can improve upon this estimate considerably using variance reduction techniques, reducing the variance by a factor of order 100 with a further, equal amount of work. The variance reduction method is a two-stage process, involving a Chebyshev approximation to the quantity in question and then the subtraction of traceless operators. The method is applied to the fermion determinant for non-perturbatively improved Wilson fermions on a 16 3 x 32 lattice. It is also applicable to a wider class of matrix operators. Finally we discuss how dynamical quark effects may be simulated in a Monte Carlo process with an effective partitioning of low and high eigenmodes. This may be done via selective updating of a trial configuration which highlights the physically relevant effects of light quark modes. (author)
Holographic study of the QCD matter under external conditions
Directory of Open Access Journals (Sweden)
Katanaeva Alisa
2017-01-01
We use methods of the bottom-up AdS/QCD approach to bring out the phase structure of several holographic models in which transition to a deconfined phase is related to a (first order Hawking-Page phase transition. The impact of phenomenological model parameters on the critical temperature and chemical potential is studied in detail. Comparison of the model predictions with results of experimental investigations, lattice QCD simulations and other methods is also done.
Thermo-magnetic effects in quark matter: Nambu-Jona-Lasinio model constrained by lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Farias, Ricardo L.S. [Universidade Federal de Santa Maria, Departamento de Fisica, Santa Maria, RS (Brazil); Kent State University, Physics Department, Kent, OH (United States); Timoteo, Varese S. [Universidade Estadual de Campinas (UNICAMP), Grupo de Optica e Modelagem Numerica (GOMNI), Faculdade de Tecnologia, Limeira, SP (Brazil); Avancini, Sidney S.; Pinto, Marcus B. [Universidade Federal de Santa Catarina, Departamento de Fisica, Florianopolis, Santa Catarina (Brazil); Krein, Gastao [Universidade Estadual Paulista, Instituto de Fisica Teorica, Sao Paulo, SP (Brazil)
2017-05-15
The phenomenon of inverse magnetic catalysis of chiral symmetry in QCD predicted by lattice simulations can be reproduced within the Nambu-Jona-Lasinio model if the coupling G of the model decreases with the strength B of the magnetic field and temperature T. The thermo-magnetic dependence of G(B, T) is obtained by fitting recent lattice QCD predictions for the chiral transition order parameter. Different thermodynamic quantities of magnetized quark matter evaluated with G(B, T) are compared with the ones obtained at constant coupling, G. The model with G(B, T) predicts a more dramatic chiral transition as the field intensity increases. In addition, the pressure and magnetization always increase with B for a given temperature. Being parametrized by four magnetic-field-dependent coefficients and having a rather simple exponential thermal dependence our accurate ansatz for the coupling constant can be easily implemented to improve typical model applications to magnetized quark matter. (orig.)
Spectroscopy of doubly and triply-charmed baryons from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Padmanath, M. [Tata Institute; Edwards, Robert G. [JLAB; Mathur, Nilmani [Tata Institute; Peardon, Michael [Trinity College, Dublin
2013-11-01
We present the ground and excited state spectra of doubly and triply-charmed baryons by using lattice QCD with dynamical clover fermions. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) Ⓧ O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses. Using those splittings for doubly-charmed baryons, and taking input of experimental Bc meson mass, we predict the mass splittings of B*c-Bc to be about 80 ± 8 MeV and mΩccb=8050±10 MeV.
K$\\to \\pi\\pi$ Amplitudes from Lattice QCD with a Light Charm Quark
Giusti, Leonardo; Laine, M; Peña, C; Wennekers, J; Wittig, H
2007-01-01
We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light (GIM limit). The low-energy constants are extracted by comparing the predictions of finite volume chiral perturbation theory with lattice QCD computations of suitable correlation functions carried out with quark masses ranging from a few MeV up to half of the physical strange mass. We observe a large DeltaI=1/2 enhancement in this corner of the parameter space of the theory. Although matching with the experimental result is not observed for the DeltaI=1/2 amplitude, our computation suggests large QCD contributions to the physical DeltaI=1/2 rule in the GIM limit, and represents the first step to quantify the role of the charm quark-mass in K-->pipi amplitudes.
Pseudoscalar decay constants from N{sub f}=2+1+1 twisted mass lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Farchioni, Federico [Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Herdoiza, Gregorio; Jansen, Karl; Nube, Andreas [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Petschlies, Marcus [Humboldt-Univ., Berlin (Germany). Inst. fuer Physik; Urbach, Carsten [Bonn Univ. (Germany). Helmholtz-Inst. fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics
2010-12-15
We present first results for the pseudoscalar decay constants f{sub K}, f{sub D} and f{sub D{sub S}} from lattice QCD with N{sub f} = 2 + 1 + 1 flavours of dynamical quarks. The lattice simulations have been performed by the European Twisted Mass collaboration (ETMC) using maximally twisted mass quarks. For the pseudoscalar decay constants we follow a mixed action approach by using so called Osterwalder-Seiler fermions in the valence sector for strange and charm quarks. The data for two values of the lattice spacing and several values of the up/down quark mass is analysed using chiral perturbation theory. (orig.)
Lattice QCD with mixed action - Borici-Creutz valence quark on staggered sea
Basak, Subhasish; Goswami, Jishnu; Chakrabarti, Dipankar
2018-03-01
Mixed action lattice QCD with Borici-Creutz valence quarks on staggered sea is investigated. The counter terms in Borici-Creutz action are fixed nonperturbatively to restore the broken symmetries. On symmetry restoration, the usual signatures of partial quenching / unitarity violation like negative scalar correlator are observed. The size of unitarity violation due to different discretization of valence and sea quark is determined by measuring Δmix.
3D Relativistic Hydrodynamic Computations Using Lattice-QCD-Inspired Equations of State
International Nuclear Information System (INIS)
Hama, Yogiro; Andrade, Rone P.G.; Grassi, Frederique; Socolowski, Otavio; Kodama, Takeshi; Tavares, Bernardo; Padula, Sandra S.
2006-01-01
In this communication, we report results of three-dimensional hydrodynamic computations, by using equations of state with a critical end point as suggested by the lattice QCD. Some of the results are an increase of the multiplicity in the mid-rapidity region and a larger elliptic-flow parameter v 2 . We discuss also the effcts of the initial-condition fluctuations and the continuous emission
3D Relativistic Hydrodynamic Computations Using Lattice-QCD-Inspired Equations of State
Energy Technology Data Exchange (ETDEWEB)
Hama, Yogiro [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Andrade, Rone P.G. [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Grassi, Frederique [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Socolowski, Otavio [Instituto Tecnologico da Aeronautica (Brazil); Kodama, Takeshi [Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil); Tavares, Bernardo [Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil); Padula, Sandra S. [Instituto de Fisica Teorica, Universidade Estadual Paulista (Brazil)
2006-08-07
In this communication, we report results of three-dimensional hydrodynamic computations, by using equations of state with a critical end point as suggested by the lattice QCD. Some of the results are an increase of the multiplicity in the mid-rapidity region and a larger elliptic-flow parameter v{sub 2}. We discuss also the effcts of the initial-condition fluctuations and the continuous emission.
Working Group Report: Lattice Field Theory
Energy Technology Data Exchange (ETDEWEB)
Blum, T.; et al.,
2013-10-22
This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.
Heavy-light mesons in lattice HQET and QCD
International Nuclear Information System (INIS)
Guazzini, D.
2007-12-01
We present a study of a combination of HQET and relativistic QCD to extract the b-quark mass and the B s -meson decay constant from lattice quenched simulations. We start from a small volume, where one can directly simulate the b-quark, and compute the connection to a large volume, where finite size effects are negligible, through a finite size technique. The latter consists of steps extrapolated to the continuum limit, where the b-region is reached through interpolations guided by the effective theory. With the lattice spacing given in terms of the Sommer's scale r 0 and the experimental B s and K masses, we get the final results for the renormalization group invariant mass M b =6.88(10) GeV, translating into anti m b (anti m b )=4.42(6) GeV in the MS scheme, and f B s =191(6) MeV for the decay constant. A renormalization condition for the chromo-magnetic operator, responsible, at leading order in the heavy quark mass expansion of HQET, for the mass splitting between the pseudoscalar and the vector channel in mesonic heavy-light bound states, is provided in terms of lattice correlations functions which well suits a non-perturbative computation involving a large range of renormalization scales and no valence quarks. The two-loop expression of the corresponding anomalous dimension in the Schroedinger functional (SF) scheme is computed starting from results in the literature; it requires a one-loop calculation in the SF scheme with a non-vanishing background field. The cutoff effects affecting the scale evolution of the renormalization factors are studied at one-loop order, and confirmed by non-perturbative quenched computations to be negligible for the numerical precision achievable at present. (orig.)
Heavy-light mesons in lattice HQET and QCD
Energy Technology Data Exchange (ETDEWEB)
Guazzini, D.
2007-12-15
We present a study of a combination of HQET and relativistic QCD to extract the b-quark mass and the B{sub s}-meson decay constant from lattice quenched simulations. We start from a small volume, where one can directly simulate the b-quark, and compute the connection to a large volume, where finite size effects are negligible, through a finite size technique. The latter consists of steps extrapolated to the continuum limit, where the b-region is reached through interpolations guided by the effective theory. With the lattice spacing given in terms of the Sommer's scale r{sub 0} and the experimental B{sub s} and K masses, we get the final results for the renormalization group invariant mass M{sub b}=6.88(10) GeV, translating into anti m{sub b}(anti m{sub b})=4.42(6) GeV in the MS scheme, and f{sub B{sub s}}=191(6) MeV for the decay constant. A renormalization condition for the chromo-magnetic operator, responsible, at leading order in the heavy quark mass expansion of HQET, for the mass splitting between the pseudoscalar and the vector channel in mesonic heavy-light bound states, is provided in terms of lattice correlations functions which well suits a non-perturbative computation involving a large range of renormalization scales and no valence quarks. The two-loop expression of the corresponding anomalous dimension in the Schroedinger functional (SF) scheme is computed starting from results in the literature; it requires a one-loop calculation in the SF scheme with a non-vanishing background field. The cutoff effects affecting the scale evolution of the renormalization factors are studied at one-loop order, and confirmed by non-perturbative quenched computations to be negligible for the numerical precision achievable at present. (orig.)
Towards the chiral limit in QCD
International Nuclear Information System (INIS)
Shailesh Chandrasekharan
2006-01-01
Computing hadronic observables by solving QCD from first principles with realistic quark masses is an important challenge in fundamental nuclear and particle physics research. Although lattice QCD provides a rigorous framework for such calculations many difficulties arise. Firstly, there are no good algorithms to solve lattice QCD with realistically light quark masses. Secondly, due to critical slowing down, Monte Carlo algorithms are able to access only small lattice sizes on coarse lattices. Finally, due to sign problems it is almost impossible to study the physics of finite baryon density. Lattice QCD contains roughly three mass scales: the cutoff (or inverse lattice spacing) a -1 , the confinement scale Λ QCD , and the pion mass m π . Most conventional Monte Carlo algorithms for QCD become inefficient in two regimes: when Λ QCD becomes small compared to a -1 and when m π becomes small compared to Λ QCD . The former can be largely controlled by perturbation theory thanks to asymptotic freedom. The latter is more difficult since chiral extrapolations are typically non-analytic and can be unreliable if the calculations are not done at sufficiently small quark masses. For this reason it has been difficult to compute quantities close to the chiral limit. The essential goal behind this proposal was to develop a new approach towards understanding QCD and QCD-like theories with sufficiently light quarks. The proposal was based on a novel cluster algorithm discovered in the strong coupling limit with staggered fermions [1]. This algorithm allowed us to explore the physics of exactly massless quarks and as well as light quarks. Thus, the hope was that this discovery would lead to the complete solution of at least a few strongly coupled QCD-like theories. The solution would be far better than those achievable through conventional methods and thus would be able to shed light on the chiral physics from a new direction. By the end of the funding period, the project led
Nucleon, Δ and Ω excited state spectra in Nf=2+1 lattice QCD
International Nuclear Information System (INIS)
Bulava, J.; Edwards, R.G.; Joo, B.; Richards, D.G.; Engelson, E.; Wallace, S.J.; Lin, H.W.; Morningstar, C.
2010-04-01
The energies of the excited states of the Nucleon, Δ and Ω and are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculation is performed at three values of the light quark mass, corresponding to pion masses m π =392(4), 438(3) and 521(3) MeV. We employ the variational method with a large basis of interpolating operators enabling six energies in each irreducible representation of the lattice to be distinguished clearly. We compare our calculation with the low-lying experimental spectrum, with which we nd reasonable agreement in the pattern of states. The need to include operators that couple to the expected multi-hadron states in the spectrum is clearly identified. (orig.)
Lattice QCD simulations on big cats, sea monsters and clock towers
Energy Technology Data Exchange (ETDEWEB)
Joo, Balint, E-mail: bjoo@jlab.or [Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)
2009-07-01
We present details of lattice QCD computations we are performing on the Cray XT series of computers, from BigBen - an XT3 hosted at the Pittsburgh Supercomputing Center (PSC) - through Jaguar (XT4) and Kraken (XT5) - which are hosted at the National Center for Computational Science (NCCS) and the National Institute of Computational Science (NICS), respectively, at Oak Ridge National Laboratory (ORNL). We discuss algorithmic tuning to make the computation more efficient and present some recent results.
Lattice QCD simulations on big cats, sea monsters and clock towers
International Nuclear Information System (INIS)
Joo, Balint
2009-01-01
We present details of lattice QCD computations we are performing on the Cray XT series of computers, from BigBen - an XT3 hosted at the Pittsburgh Supercomputing Center (PSC) - through Jaguar (XT4) and Kraken (XT5) - which are hosted at the National Center for Computational Science (NCCS) and the National Institute of Computational Science (NICS), respectively, at Oak Ridge National Laboratory (ORNL). We discuss algorithmic tuning to make the computation more efficient and present some recent results.
Isospin Splittings in the Light-Baryon Octet from Lattice QCD and QED
Borsanyi, Sz.; Dürr, S.; Fodor, Z.; Frison, J.; Hoelbling, C.; Katz, S. D.; Krieg, S.; Kurth, Th.; Lellouch, L.; Lippert, Th.; Portelli, A.; Ramos, A.; Sastre, A.; Szabo, K.; Budapest-Marseille-Wuppertal Collaboration
2013-12-01
While electromagnetic and up-down quark mass difference effects on octet baryon masses are very small, they have important consequences. The stability of the hydrogen atom against beta decay is a prominent example. Here, we include these effects by adding them to valence quarks in a lattice QCD calculation based on Nf=2+1 simulations with five lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and average up-down quark masses all the way down to their physical value. This allows us to gain control over all systematic errors, except for the one associated with neglecting electromagnetism in the sea. We compute the octet baryon isomultiplet mass splittings, as well as the individual contributions from electromagnetism and the up-down quark mass difference. Our results for the total splittings are in good agreement with experiment.
Short-distance matrix elements for $D$-meson mixing for 2+1 lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Chang, Chia Cheng [Univ. of Illinois, Champaign, IL (United States)
2015-01-01
We study the short-distance hadronic matrix elements for D-meson mixing with partially quenched N_{f} = 2+1 lattice QCD. We use a large set of the MIMD Lattice Computation Collaboration's gauge configurations with a^{2} tadpole-improved staggered sea quarks and tadpole-improved Lüscher-Weisz gluons. We use the a^{2} tadpole-improved action for valence light quarks and the Sheikoleslami-Wohlert action with the Fermilab interpretation for the valence charm quark. Our calculation covers the complete set of five operators needed to constrain new physics models for D-meson mixing. We match our matrix elements to the MS-NDR scheme evaluated at 3 GeV. We report values for the Beneke-Buchalla-Greub-Lenz-Nierste choice of evanescent operators.
Scattering phase shift for elastic two pion scattering and the rho resonance in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gutzwiller, Simone
2012-10-08
In this thesis we use lattice QCD to compute scattering phase shifts for elastic two-pion scattering in the isospin I=1 channel. Using Luescher's formalism, we derive the scattering phase shifts for different total momenta of the two-pion system in a non-rest frame. Furthermore we analyse the symmetries of the non-rest frame lattices and construct 2-pion and rho operators transforming in accordance with these symmetries. The data was collected for a 32{sup 3} x 64 and a 40{sup 3} x 64 lattice with N{sub f}=2 clover improved Wilson fermions at a pion mass around 290 MeV and a lattice spacing of about 0.072 fm.
Scattering phase shift for elastic two pion scattering and the rho resonance in lattice QCD
International Nuclear Information System (INIS)
Gutzwiller, Simone
2012-01-01
In this thesis we use lattice QCD to compute scattering phase shifts for elastic two-pion scattering in the isospin I=1 channel. Using Luescher's formalism, we derive the scattering phase shifts for different total momenta of the two-pion system in a non-rest frame. Furthermore we analyse the symmetries of the non-rest frame lattices and construct 2-pion and rho operators transforming in accordance with these symmetries. The data was collected for a 32 3 x 64 and a 40 3 x 64 lattice with N f =2 clover improved Wilson fermions at a pion mass around 290 MeV and a lattice spacing of about 0.072 fm.
Light hadrons from lattice QCD with light (u,d), strange and charm dynamical quarks
Energy Technology Data Exchange (ETDEWEB)
Baron, R. [CEA, Centre de Saclay, 91 - Gif-sur-Yvette (France). IRFU/Service de Physique Nucleaire; Boucaud, P. [CNRS et Paris-Sud 11 Univ., 91 - Orsay (France). Lab. de Physique Theorique; Carbonell, J. [Lab. de Physique Subatomique et Cosmologie, 38 - Grenoble (FR)] (and others)
2010-04-15
We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (N{sub f}=2+1+1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark masses is performed at two values of the lattice spacing a {approx} 0:078 fm and a {approx}0.086 fm with lattice sizes ranging from L{approx}1.9 fm to L{approx}2.8 fm. We measure with high statistical precision the light pseudoscalar mass m{sub PS} and decay constant f{sub PS} in a range 270
Hadron spectrum in quenched lattice QCD and distribution of zero modes
International Nuclear Information System (INIS)
Iwasaki, Yoichi
1989-01-01
I report the results of the calculation of the hadron spectrum with the standard one-plaquette gauge action on a 16 3 x48 lattice at β=5.85 in the quenched lattice QCD. The result remarkably agrees with that of quark potential models for the case where the quark mass is equal to or is larger than the strange quark mass, even when one uses the standard one-plaquette gauge action. This is contrary to what is stated in the literature. We clarify the reason of the discrepancy, paying close attention to systematic errors in numerical calculations. Further, I show the distribution of zero modes of quark matrix, both in the cases of a RG improved gauge action and the standard action, and discuss the difference between the two cases. (orig.)
Excited-state spectroscopy of singly, doubly and triply-charmed baryons from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Padmanath, M. [Tata Institute; Edwards, Robert G. [JLAB; Mathur, Nilmani [Tata Institute; Peardon, Michael [Trinity College
2014-07-01
We present the ground and excited state spectra of singly, doubly and triply-charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. These operators transform as irreducible representations of SU(3)F symmetry for flavour, SU(4) symmetry for Dirac spins of quarks and O(3) symmetry for orbital angular momenta. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6)ⓍO(3) symmetry.
Scientific articles of the RBRC/CCAST Symposium on Spin Physics Lattice QCD and RHIC Physics
International Nuclear Information System (INIS)
2003-01-01
This volume comprises scientific articles of the symposium on spin physics, lattice QCD and RHIC physics organized by RIKEN BNL research center (RBRC) and China center of advanced science and technology (CCAST). The talks were discussing the spin structure of nucleons and other problems of RHIC physics
Tetraquark resonances computed with static lattice QCD potentials and scattering theory
Directory of Open Access Journals (Sweden)
Bicudo Pedro
2018-01-01
Full Text Available We study tetraquark resonances with lattice QCD potentials computed for two static quarks and two dynamical quarks, the Born-Oppenheimer approximation and the emergent wave method of scattering theory. As a proof of concept we focus on systems with isospin I = 0, but consider different relative angular momenta l of the heavy b quarks. We compute the phase shifts and search for S and T matrix poles in the second Riemann sheet. We predict a new tetraquark resonance for l = 1, decaying into two B mesons, with quantum numbers I(JP = 0(1−, mass m=10576−4+4 MeV and decay width Γ=112−103+90 MeV.
Non-perturbative studies of QCD at small quark masses
Energy Technology Data Exchange (ETDEWEB)
Wennekers, J.
2006-07-15
We investigate the quenched approximation of lattice QCD with numerical simulations of Ginsparg-Wilson fermions, which are a fermion discretisation with exact chiral symmetry. We compute the renormalisation constant of the scalar density, which allows to extrapolate the chiral condensate to the continuum limit. Furthermore we match lattice results of matrix elements describing hadronic kaon decays to Chiral Perturbation Theory in finite volume and at almost vanishing quark mass. The resulting low-energy constants in the considered SU(4)-flavour symmetric case indicate a substantial contribution of low scale QCD effects to the {delta}I = 1/2 rule. (Orig.)
Decay Constants of B and D Mesons from Non-pertubatively Improved Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
K.C. Bowler; L. Del Debbio; J.M. Flynn; G.N, Lacagnina; V.I. Lesk; C.M. Maynard; D.G. Richards
2000-07-01
The decay constants of B and D mesons are computed in quenched lattice QCD at two different values of the coupling. The action and operators are ? (a) improved with non-perturbative coefficients where available. The results and systematic errors are discussed in detail. Results for vector decay constants, flavour symmetry breaking ratios of decay constants, the pseudoscalar-vector mass splitting and D meson masses are also presented.
Energy Technology Data Exchange (ETDEWEB)
Molina, Raquel [Univ. of Sao Paulo (Brazil); Hu, Bitao [George Washington Univ., Washington, DC (United States); Doering, Michael [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); George Washington Univ., Washington, DC (United States); Mai, Maxim [George Washington Univ., Washington, DC (United States); Alexandru, Andrei [George Washington Univ., Washington, DC (United States)
2018-04-01
Several lattice QCD simulations of meson-meson scattering in p-wave and Isospin = 1 in Nf = 2 + 1 flavours have been carried out recently. Unitarized Chiral Perturbation Theory is used to perform extrapolations to the physical point. In contrast to previous findings on the analyses of Nf = 2 lattice data, where most of the data seems to be in agreement, some discrepancies are detected in the Nf = 2 + 1 lattice data analyses, which could be due to different masses of the strange quark, meson decay constants, initial constraints in the simulation, or other lattice artifacts. In addition, the low-energy constants are compared to the ones from a recent analysis of Nf = 2 lattice data.
Non-perturbative test of the Witten-Veneziano formula from lattice QCD
International Nuclear Information System (INIS)
Cichy, Krzysztof; Jansen, Karl; Ottnad, Konstantin; Urbach, Carsten; Bonn Univ.
2015-10-01
We compute both sides of the Witten-Veneziano formula using lattice techniques. For the one side we perform dedicated quenched simulations and use the spectral projector method to determine the topological susceptibility in the pure Yang-Mills theory. The other side we determine in lattice QCD with N f =2 +1+1 dynamical Wilson twisted mass fermions including for the first time also the flavour singlet decay constant. The Witten-Veneziano formula represents a leading order expression in the framework of chiral perturbation theory and we also employ leading order chiral perturbation theory to relate the flavor singlet decay constant to the relevant decay constant parameters in the quark flavor basis and flavor non-singlet decay constants. After taking the continuum and the SU(2) chiral limits we compare both sides and find good agreement within uncertainties.
Lambda-bar, lambda(1) and m(b) in three-flavor (lattice) QCD
International Nuclear Information System (INIS)
Freeland, Elizabeth D.; Art Inst. of Chicago; Kronfeld, Andreas S.; Simone, James N.; Van de Water, Ruth S.; Fermilab
2006-01-01
The heavy-quark expansion for inclusive semi-leptonic B decays introduces Λ and λ1 , which are matrix elements in heavy-quark effective field theory. We review how they can be obtained from an analysis of the heavy quark mass dependence of heavy-light meson masses in lattice QCD. We present preliminary results for the bottom quark mass, mb, using Λ and λ1 for the Bs meson from a 2+1 sea-flavor unquenched calculation
Lattice QCD Thermodynamics First 5000 Trajectories
International Nuclear Information System (INIS)
Soltz, R; Gupta, R
2007-01-01
These results represent the first LQCD analysis for approximately 5000 trajectories with each of the p4rhmc and milc codes, with some of the lower temperature runs having fewer. Both runs were for lattice dimensions of 32 3 x8. Some 32 4 T=0 jobs were also run for p4rhmc. The p4 calculation was performed with v2.0 QMP( ) MPI.X (semi-optimized p4 code using qmp over mpi) and milc version of the su3 rhmc susc eos executable dated Mar 1, 2007 on ubgl in the /usr/gapps/hip/qcd/milc/bin subdirectory (svn revision 28). As with previous runs, calculations were performed along lines of constant physics, with the light quark masses 2-3 times their physics values and the strange quark mass set by m ud = 0.1m s . Job submissions were performed using a new subSet.pl job submission script that locates current jobs and submits additional jobs with the same beta value as pending. Note that after reaching a limit of about 35 jobs subsequent submissions are delayed and will not be submitted directly from that state. The job submission script was used to submit revised versions of the milc and p4rhmc csh scripts. Initial thermalized lattices for each code were also for milc (taken from the firstPhys runs), but the p4rhmc runs include thermalization. The only modifications for running on BG/L were to the directory names and the mT parameter which determines job durations (24 hrs on BG/L vs. 4 hrs on ubgl). All finite temperature jobs were submitted to the 512 node partitions, and all T=0 runs were submitted to 2048 node partitions. The set of runs was plagued by filesystem errors on lscratch1 and lscratcH 2 . Many jobs had to be reset (deleting the most recent output file for milc and/or lattice for p4) and resubmitted. The analysis was performed with a new set of scripts that produced a more condensed output for scanning. All scans were verified with checksums, which have been retained in the output along with the line numbers. All lattices, log files, and job submission scripts
Zou, You-Hao; Zhang, Jian-Bo; Xiong, Guang-Yi; Chen, Ying; Liu, Chuan; Liu, Yu-Bin; Ma, Jian-Ping
2017-10-01
The topological charge density and topological susceptibility are determined by a multi-probing approximation using overlap fermions in quenched SU(3) gauge theory. Then we investigate the topological structure of the quenched QCD vacuum, and compare it with results from the all-scale topological density. The results are consistent. Random permuted topological charge density is used to check whether these structures represent underlying ordered properties. The pseudoscalar glueball mass is extracted from the two-point correlation function of the topological charge density. We study 3 ensembles of different lattice spacing a with the same lattice volume 163×32. The results are compatible with the results of all-scale topological charge density, and the topological structures revealed by multi-probing are much closer to all-scale topological charge density than those from eigenmode expansion. Supported by National Natural Science Foundation of China (NSFC) (11335001, 11275169, 11075167), It is also supported in part by the DFG and the NSFC (11261130311) through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD". This work was also funded in part by National Basic Research Program of China (973 Program) (2015CB856700)
Energy- and cost-efficient lattice-QCD computations using graphics processing units
Energy Technology Data Exchange (ETDEWEB)
Bach, Matthias
2014-07-01
Quarks and gluons are the building blocks of all hadronic matter, like protons and neutrons. Their interaction is described by Quantum Chromodynamics (QCD), a theory under test by large scale experiments like the Large Hadron Collider (LHC) at CERN and in the future at the Facility for Antiproton and Ion Research (FAIR) at GSI. However, perturbative methods can only be applied to QCD for high energies. Studies from first principles are possible via a discretization onto an Euclidean space-time grid. This discretization of QCD is called Lattice QCD (LQCD) and is the only ab-initio option outside of the high-energy regime. LQCD is extremely compute and memory intensive. In particular, it is by definition always bandwidth limited. Thus - despite the complexity of LQCD applications - it led to the development of several specialized compute platforms and influenced the development of others. However, in recent years General-Purpose computation on Graphics Processing Units (GPGPU) came up as a new means for parallel computing. Contrary to machines traditionally used for LQCD, graphics processing units (GPUs) are a massmarket product. This promises advantages in both the pace at which higher-performing hardware becomes available and its price. CL2QCD is an OpenCL based implementation of LQCD using Wilson fermions that was developed within this thesis. It operates on GPUs by all major vendors as well as on central processing units (CPUs). On the AMD Radeon HD 7970 it provides the fastest double-precision D kernel for a single GPU, achieving 120GFLOPS. D - the most compute intensive kernel in LQCD simulations - is commonly used to compare LQCD platforms. This performance is enabled by an in-depth analysis of optimization techniques for bandwidth-limited codes on GPUs. Further, analysis of the communication between GPU and CPU, as well as between multiple GPUs, enables high-performance Krylov space solvers and linear scaling to multiple GPUs within a single system. LQCD
Energy- and cost-efficient lattice-QCD computations using graphics processing units
International Nuclear Information System (INIS)
Bach, Matthias
2014-01-01
Quarks and gluons are the building blocks of all hadronic matter, like protons and neutrons. Their interaction is described by Quantum Chromodynamics (QCD), a theory under test by large scale experiments like the Large Hadron Collider (LHC) at CERN and in the future at the Facility for Antiproton and Ion Research (FAIR) at GSI. However, perturbative methods can only be applied to QCD for high energies. Studies from first principles are possible via a discretization onto an Euclidean space-time grid. This discretization of QCD is called Lattice QCD (LQCD) and is the only ab-initio option outside of the high-energy regime. LQCD is extremely compute and memory intensive. In particular, it is by definition always bandwidth limited. Thus - despite the complexity of LQCD applications - it led to the development of several specialized compute platforms and influenced the development of others. However, in recent years General-Purpose computation on Graphics Processing Units (GPGPU) came up as a new means for parallel computing. Contrary to machines traditionally used for LQCD, graphics processing units (GPUs) are a massmarket product. This promises advantages in both the pace at which higher-performing hardware becomes available and its price. CL2QCD is an OpenCL based implementation of LQCD using Wilson fermions that was developed within this thesis. It operates on GPUs by all major vendors as well as on central processing units (CPUs). On the AMD Radeon HD 7970 it provides the fastest double-precision D kernel for a single GPU, achieving 120GFLOPS. D - the most compute intensive kernel in LQCD simulations - is commonly used to compare LQCD platforms. This performance is enabled by an in-depth analysis of optimization techniques for bandwidth-limited codes on GPUs. Further, analysis of the communication between GPU and CPU, as well as between multiple GPUs, enables high-performance Krylov space solvers and linear scaling to multiple GPUs within a single system. LQCD
From Kondo model and strong coupling lattice QCD to the Isgur-Wise function
International Nuclear Information System (INIS)
Patel, Apoorva
1995-01-01
Isgur-Wise functions parametrise the leading behaviour of weak decay form factors of mesons and baryons containing a single heavy quark. The form factors for the quark mass operator are calculated in strong coupling lattice QCD, and Isgur-Wise functions extracted from them. Based on renormalisation group invariance of the operators involved, it is argued that the Isgur-Wise functions would be the same in the weak coupling continuum theory. (author)
Critical point of Nf=3 QCD from lattice simulations in the canonical ensemble
International Nuclear Information System (INIS)
Li Anyi; Alexandru, Andrei; Liu, Keh-Fei
2011-01-01
A canonical ensemble algorithm is employed to study the phase diagram of N f =3 QCD using lattice simulations. We lock in the desired quark number sector using an exact Fourier transform of the fermion determinant. We scan the phase space below T c and look for an S-shape structure in the chemical potential, which signals the coexistence phase of a first order phase transition in finite volume. Applying Maxwell construction, we determine the boundaries of the coexistence phase at three temperatures and extrapolate them to locate the critical point. Using an improved gauge action and improved Wilson fermions on lattices with a spatial extent of 1.8 fm and quark masses close to that of the strange, we find the critical point at T E =0.925(5)T c and baryon chemical potential μ B E =2.60(8)T c .
B physics from HQET in two-flavour lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Bernardoni, F. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Blossier, B. [Paris-11 Univ., Orsay (France). Lab. de Physique Theorique; Bulava, J. [CERN, Geneva (Switzerland). Physics Department] [and others; Collaboration: ALPHA Collaboration
2012-11-15
We present our analysis of B physics quantities using non-perturbatively matched Heavy Quark Effective Theory (HQET) in N{sub f}=2 lattice QCD on the CLS ensembles. Using all-to-all propagators, HYP-smeared static quarks, and the Generalized Eigenvalue Problem (GEVP) approach with a conservative plateau selection procedure, we are able to systematically control all sources of error. With significantly increased statistics compared to last year, our preliminary results are anti m{sub b}(anti m{sub b})=4.22(10)(4){sub z} GeV for the MS b-quark mass, and f{sub B}=193(9){sub stat}(4){sub {chi}} MeV and f{sub B{sub s}}=219(12){sub stat} MeV for the B-meson decay constants.
Meson-Baryon Scattering Lengths from Mixed-Action Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Will Detmold, William Detmold, Konstantinos Orginos, Aaron Torok, Silas R Beane, Thomas C Luu, Assumpta Parreno, Martin Savage, Andre Walker-Loud
2010-04-01
The $\\pi^+\\Sigma^+$, $\\pi^+\\Xi^0$ , $K^+p$, $K^+n$, and $K^0 \\Xi^0$ scattering lengths are calculated in mixed-action Lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations at four light-quark masses, and at two light-quark masses on the fine MILC configurations. Heavy Baryon Chiral Perturbation Theory with two and three flavors of light quarks is used to perform the chiral extrapolations. We find no convergence for the kaon-baryon processes in the three-flavor chiral expansion. Using the two-flavor chiral expansion, we find $a_{\\pi^+\\Sigma^+} = ?0.197 ± 0.017$ fm, and $a_{\\pi^+\\Xi^0} = ?0.098 0.017$ fm, where the comprehensive error includes statistical and systematic uncertainties.
The strong coupling constant of QCD with four flavors
Energy Technology Data Exchange (ETDEWEB)
Tekin, Fatih
2010-11-01
In this thesis we study the theory of strong interaction Quantum Chromodynamics on a space-time lattice (lattice QCD) with four flavors of dynamical fermions by numerical simulations. In the early days of lattice QCD, only pure gauge field simulations were accessible to the computational facilities and the effects of quark polarization were neglected. The so-called fermion determinant in the path integral was set to one (quenched approximation). The reason for this approximation was mainly the limitation of computational power because the inclusion of the fermion determinant required an enormous numerical effort. However, for full QCD simulations the virtual quark loops had to be taken into account and the development of new machines and new algorithmic techniques made the so-called dynamical simulations with at least two flavors possible. In recent years, different collaborations studied lattice QCD with dynamical fermions. In our project we study lattice QCD with four degenerated flavors of O(a) improved Wilson quarks in the Schroedinger functional scheme and calculate the energy dependence of the strong coupling constant. For this purpose, we determine the O(a) improvement coefficient c{sub sw} with four flavors and use this result to calculate the step scaling function of QCD with four flavors which describes the scale evolution of the running coupling. Using a recursive finite-size technique, the {lambda} parameter is determined in units of a technical scale L{sub max} which is an unambiguously defined length in the hadronic regime. The coupling {alpha}{sub SF} of QCD in the so-called Schroedinger functional scheme is calculated over a wide range of energies non-perturbatively and compared with 2-loop and 3-loop perturbation theory as well as with the non-perturbative result for only two flavors. (orig.)
The strong coupling constant of QCD with four flavors
International Nuclear Information System (INIS)
Tekin, Fatih
2010-01-01
In this thesis we study the theory of strong interaction Quantum Chromodynamics on a space-time lattice (lattice QCD) with four flavors of dynamical fermions by numerical simulations. In the early days of lattice QCD, only pure gauge field simulations were accessible to the computational facilities and the effects of quark polarization were neglected. The so-called fermion determinant in the path integral was set to one (quenched approximation). The reason for this approximation was mainly the limitation of computational power because the inclusion of the fermion determinant required an enormous numerical effort. However, for full QCD simulations the virtual quark loops had to be taken into account and the development of new machines and new algorithmic techniques made the so-called dynamical simulations with at least two flavors possible. In recent years, different collaborations studied lattice QCD with dynamical fermions. In our project we study lattice QCD with four degenerated flavors of O(a) improved Wilson quarks in the Schroedinger functional scheme and calculate the energy dependence of the strong coupling constant. For this purpose, we determine the O(a) improvement coefficient c sw with four flavors and use this result to calculate the step scaling function of QCD with four flavors which describes the scale evolution of the running coupling. Using a recursive finite-size technique, the Λ parameter is determined in units of a technical scale L max which is an unambiguously defined length in the hadronic regime. The coupling α SF of QCD in the so-called Schroedinger functional scheme is calculated over a wide range of energies non-perturbatively and compared with 2-loop and 3-loop perturbation theory as well as with the non-perturbative result for only two flavors. (orig.)
Investigations of chiral symmetry breaking and topological aspects of lattice QCD
International Nuclear Information System (INIS)
Garcia Ramos, Elena
2013-01-01
The spontaneous breaking of chiral symmetry is a fascinating phenomenon of QCD whose mechanism is still not well understood and it has fundamental phenomenological implications. It is, for instance, responsible for the low mass of the pions which are effectively Goldstone bosons of the spontaneously broken symmetry. Since these phenomena belong to the low energy regime of QCD, non-perturbative techniques have to be applied in order to study them. In this work we use the twisted mass lattice QCD regularization to compute the chiral condensate, the order parameter of spontaneous chiral symmetry breaking. To this end we apply the recently introduced method of spectral projectors which allows us to perform calculations in large volumes due to its inherently low computational cost. This approach, moreover, enables a direct calculation of the chiral condensate based on a theoretically clean definition of the observable via density chains. We thus present a continuum limit determination of the chirally extrapolated condensate for N f =2 and N f =2+1+1 flavours of twisted mass fermions at maximal twist. In addition we study the chiral behavior of the topological susceptibility, a measure of the topological fluctuations of the gauge fields. We again apply the spectral projector method for this calculation. We comment on the difficulties which appear in the calculation of this observable due to the large autocorrelations involved. Finally we present the continuum limit result of the topological susceptibility in the pure gluonic theory which allows us to perform a test of the Witten-Veneziano relation. We found that this relation is well satisfied. Our results support the validity of the Witten-Veneziano formula which relates the topological fluctuations of the gauge fields with the unexpectedly large value of the η' mass.
Lattice QCD results for the HVP contribution to the anomalous magnetic moments of leptons
Directory of Open Access Journals (Sweden)
Borsanyi Szabolcs
2018-01-01
Full Text Available We present lattice QCD results by the Budapest-Marseille-Wuppertal (BMW Collaboration for the leading-order contribution of the hadron vacuum polarization (LOHVP to the anomalous magnetic moments of all charged leptons. Calculations are performed with u, d, s and c quarks at their physical masses, in volumes of linear extent larger than 6 fm, and at six values of the lattice spacing, allowing for controlled continuum extrapolations. All connected and disconnected contributions are calculated for not only the muon but also the electron and tau anomalous magnetic moments. Systematic uncertainties are thoroughly discussed and comparisons with other calculations and phenomenological estimates are made.
Lattice QCD results for the HVP contribution to the anomalous magnetic moments of leptons
2018-03-01
We present lattice QCD results by the Budapest-Marseille-Wuppertal (BMW) Collaboration for the leading-order contribution of the hadron vacuum polarization (LOHVP) to the anomalous magnetic moments of all charged leptons. Calculations are performed with u, d, s and c quarks at their physical masses, in volumes of linear extent larger than 6 fm, and at six values of the lattice spacing, allowing for controlled continuum extrapolations. All connected and disconnected contributions are calculated for not only the muon but also the electron and tau anomalous magnetic moments. Systematic uncertainties are thoroughly discussed and comparisons with other calculations and phenomenological estimates are made.
Phase structure of thermal lattice QCD with N{sub f} = 2 twisted mass Wilson fermions
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, E.M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Lombardo, M. P. [INFN, Laboratori Nazionali di Frascati (Italy); Mueller-Preussker, M.; Petschlies, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Philipsen, O.; Zeidlewicz, L. [Inst. fuer Theoretische Physik, Wilhelms-Univ. Muenster (Germany)
2009-09-15
We present numerical results for the phase diagram of lattice QCD at finite temperature in the formulation with twisted mass Wilson fermions and a tree-level Symanzik-improved gauge action. Our simulations are performed on lattices with temporal extent N{sub {tau}}=8, and lattice coupling {beta} ranging from strong coupling to the scaling domain. Covering a wide range in the space spanned by the lattice coupling {beta} and the hopping and twisted mass parameters {kappa} and {mu}, respectively, we obtain a comprehensive picture of the rich phase structure of the lattice theory. In particular, we verify the existence of an Aoki phase in the strong coupling region and the realisation of the Sharpe-Singleton scenario at intermediate couplings. In the weak coupling region we identify the phase boundary for the physical finite temperature phase transition/crossover. Its shape in the three-dimensional parameter space is consistent with Creutz's conjecture of a cone-shaped thermal transition surface. (orig.)
Nearly perturbative lattice-motivated QCD coupling with zero IR limit
Ayala, César; Cvetič, Gorazd; Kögerler, Reinhart; Kondrashuk, Igor
2018-03-01
The product of the gluon dressing function and the square of the ghost dressing function in the Landau gauge can be regarded to represent, apart from the inverse power corrections 1/{Q}2n, a nonperturbative generalization { \\mathcal A }({Q}2) of the perturbative QCD running coupling a({Q}2) (\\equiv {α }s({Q}2)/π ). Recent large volume lattice calculations for these dressing functions indicate that the coupling defined in such a way goes to zero as { \\mathcal A }({Q}2)∼ {Q}2 when the squared momenta Q 2 go to zero ({Q}2\\ll 1 {GeV}}2). In this work we construct such a QCD coupling { \\mathcal A }({Q}2) which fulfills also various other physically motivated conditions. At high momenta it becomes the underlying perturbative coupling a({Q}2) to a very high precision. And at intermediate low squared momenta {Q}2∼ 1 {GeV}}2 it gives results consistent with the data of the semihadronic τ lepton decays as measured by OPAL and ALEPH. The coupling is constructed in a dispersive way, resulting as a byproduct in the holomorphic behavior of { \\mathcal A }({Q}2) in the complex Q 2-plane which reflects the holomorphic behavior of the spacelike QCD observables. Application of the Borel sum rules to τ-decay V + A spectral functions allows us to obtain values for the gluon (dimension-4) condensate and the dimension-6 condensate, which reproduce the measured OPAL and ALEPH data to a significantly better precision than the perturbative \\overline{MS}} coupling approach.
Lattice QCD study of the $H$ dibaryon using hexaquark and two-baryon interpolators arXiv
Francis, A.; Junnarkar, P.M.; Miao, Ch.; Rae, T.D.; Wittig, H.
We present a lattice QCD spectroscopy study in the isospin singlet, strangeness $-2$ sectors relevant for the conjectured $H$ dibaryon. We employ both hexaquark and two-baryon interpolating operators to isolate the ground state in the rest frame and in moving frames. Calculations are performed using two flavors of O($a$)-improved Wilson fermions and a quenched strange quark. Our initial point-source method for constructing correlators does not allow for two-baryon operators at the source; nevertheless, results from using these operators at the sink indicate that they provide an improved overlap onto the ground state in comparison with the hexaquark operators. We also present results, in the rest frame, using a second method based on distillation to compute a hermitian matrix of correlators with two-baryon operators at both the source and the sink. This method yields a much more precise and reliable determination of the ground-state energy. In the flavor-SU(3) symmetric case, we apply L\\"uscher's finite-volume...
Finite-temperature phase structure of lattice QCD with Wilson quark action
International Nuclear Information System (INIS)
Aoki, S.; Ukawa, A.; Umemura, T.
1996-01-01
The long-standing issue of the nature of the critical line of lattice QCD with the Wilson quark action at finite temperatures, defined to be the line of vanishing pion screening mass, and its relation to the line of finite-temperature chiral transition is examined. Presented are both analytical and numerical evidence that the critical line forms a cusp at a finite gauge coupling, and that the line of chiral transition runs past the tip of the cusp without touching the critical line. Implications on the continuum limit and the flavor dependence of chiral transition are discussed. copyright 1996 The American Physical Society
Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD.
Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram
2015-11-20
We present lattice QCD results on the neutron tensor charges including, for the first time, a simultaneous extrapolation in the lattice spacing, volume, and light quark masses to the physical point in the continuum limit. We find that the "disconnected" contribution is smaller than the statistical error in the "connected" contribution. Our estimates in the modified minimal subtraction scheme at 2 GeV, including all systematics, are g_{T}^{d-u}=1.020(76), g_{T}^{d}=0.774(66), g_{T}^{u}=-0.233(28), and g_{T}^{s}=0.008(9). The flavor diagonal charges determine the size of the neutron electric dipole moment (EDM) induced by quark EDMs that are generated in many new scenarios of CP violation beyond the standard model. We use our results to derive model-independent bounds on the EDMs of light quarks and update the EDM phenomenology in split supersymmetry with gaugino mass unification, finding a stringent upper bound of d_{n}<4×10^{-28} e cm for the neutron EDM in this scenario.
An exploratory study of heavy domain wall fermions on the lattice
Boyle, Peter; Marinkovic, Marina Krstic; Sanfilippo, Francesco; Spraggs, Matthew; Tsang, Justus Tobias
2016-01-01
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4$d$ overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of $am_h\\approx 0.4$, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range $2.0-5.7\\,\\mathrm{GeV}$. We observe very mild $a^2$ scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
ρ resonance from the I = 1 ππ potential in lattice QCD
Kawai, Daisuke
2018-03-01
We calculate the phase shift for the I = 1 ππ scattering in 2+1 flavor lattice QCD at mπ = 410 MeV, using all-to-all propagators with the LapH smearing. We first investigate the sink operator independence of the I = 2 ππ scattering phase shift to estimate the systematics in the LapH smearing scheme in the HAL QCD method at mπ = 870 MeV. The difference in the scattering phase shift in this channel between the conventional point sink scheme and the smeared sink scheme is reasonably small as long as the next-toleading analysis is employed in the smeared sink scheme with larger smearing levels. We then extract the I = 1 ππ potential with the smeared sink operator, whose scattering phase shift shows a resonant behavior (ρ resonance). We also examine the pole of the S-matrix corresponding to the ρ resonance in the complex energy plane.
Determination of csw in Nf=3+1 lattice QCD with massive Wilson fermions
International Nuclear Information System (INIS)
Fritzsch, Patrick; Stollenwerk, Felix; Wolff, Ulli; Sommer, Rainer
2015-01-01
We develop a strategy for the non-perturbative determination of the O(a)-improvement coefficient c sw for Wilson fermions with massive sea quarks. The improvement condition is defined via the PCAC relation in the Schroedinger functional. It is imposed along a line of constant physics designed to be close to the correct mass of the charm quark. The numerical work uses the tree-level improved Luescher-Weisz gauge action in N f =3+1 Lattice QCD.
Heavy quark masses in the continuum limit of quenched Lattice QCD
International Nuclear Information System (INIS)
De Divitiis, G.M.; Guagnelli, M.; Palombi, F.; Petronzio, R.; Tantalo, N.
2003-01-01
We compute charm and bottom quark masses in the quenched approximation and in the continuum limit of lattice QCD. We make use of a step scaling method, previously introduced to deal with two scale problems, that allows to take the continuum limit of the lattice data. We determine the RGI quark masses and make the connection to the MS-bar scheme. The continuum extrapolation gives us a value m b RGI =6.73(16) GeV for the b-quark and m c RGI =1.681(36) GeV for the c-quark, corresponding, respectively, to m b MS-bar (m b MS-bar =4.33(10) GeV and m c MS-bar (m c MS-bar =1.319(28) GeV. The latter result, in agreement with current estimates, is for us a check of the method. Using our results on the heavy quark masses we compute the mass of the B c meson, M B c =6.46(15) GeV
Lattice QCD Thermodynamics and RHIC-BES Particle Production within Generic Nonextensive Statistics
Tawfik, Abdel Nasser
2018-05-01
The current status of implementing Tsallis (nonextensive) statistics on high-energy physics is briefly reviewed. The remarkably low freezeout-temperature, which apparently fails to reproduce the firstprinciple lattice QCD thermodynamics and the measured particle ratios, etc. is discussed. The present work suggests a novel interpretation for the so-called " Tsallis-temperature". It is proposed that the low Tsallis-temperature is due to incomplete implementation of Tsallis algebra though exponential and logarithmic functions to the high-energy particle-production. Substituting Tsallis algebra into grand-canonical partition-function of the hadron resonance gas model seems not assuring full incorporation of nonextensivity or correlations in that model. The statistics describing the phase-space volume, the number of states and the possible changes in the elementary cells should be rather modified due to interacting correlated subsystems, of which the phase-space is consisting. Alternatively, two asymptotic properties, each is associated with a scaling function, are utilized to classify a generalized entropy for such a system with large ensemble (produced particles) and strong correlations. Both scaling exponents define equivalence classes for all interacting and noninteracting systems and unambiguously characterize any statistical system in its thermodynamic limit. We conclude that the nature of lattice QCD simulations is apparently extensive and accordingly the Boltzmann-Gibbs statistics is fully fulfilled. Furthermore, we found that the ratios of various particle yields at extreme high and extreme low energies of RHIC-BES is likely nonextensive but not necessarily of Tsallis type.
Computing K and D meson masses with N-f=2+1+1 twisted mass lattice QCD
Baron, Remi; Boucaud, Philippe; Carbonell, Jaume; Drach, Vincent; Farchioni, Federico; Herdoiza, Gregorio; Jansen, Karl; Michael, Chris; Montvay, Istvan; Pallante, Elisabetta; Pene, Olivier; Reker, Siebren; Urbach, Carsten; Wagner, Marc; Wenger, Urs
We discuss the computation of the mass of the K and D mesons within the framework of N-f = 2 + 1 + 1 twisted mass lattice QCD from a technical point of view. These quantities are essential, already at the level of generating gauge configurations, being obvious candidates to tune the strange and
Lattice Methods for Quantum Chromodynamics
DeGrand, Thomas
2006-01-01
Numerical simulation of lattice-regulated QCD has become an important source of information about strong interactions. In the last few years there has been an explosion of techniques for performing ever more accurate studies on the properties of strongly interacting particles. Lattice predictions directly impact many areas of particle and nuclear physics theory and phenomenology. This book provides a thorough introduction to the specialized techniques needed to carry out numerical simulations of QCD: a description of lattice discretizations of fermions and gauge fields, methods for actually do
A new approach to the problem of dynamical quarks in numerical simulations of lattice QCD
International Nuclear Information System (INIS)
Luescher, M.
1993-11-01
Lattice QCD with an even number of degenerate quark flavours is shown to be a limit of a local bosonic field theory. The action of the bosonic theory is real and bounded from below so that standard simulation algorithms can be expected to apply. The feasibility of such calculations is discussed, but no practical tests have yet been made. (orig.)
Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks
International Nuclear Information System (INIS)
Huey-Wen Lin; Shigemi Ohta
2006-01-01
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm) 3 . Despite the small volume, the ratio of the isovector vector and axial charges g A /g V and that of structure function moments u-d / Δ u-Δ d are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm) 3 . Even with preliminary statistics of 25-30 gauge configurations, the ratios g A /g V and u-d / Δu - Δd are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d 1 , though yet to be renormalized, appears small in both sets
NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS
International Nuclear Information System (INIS)
LIN, H.W.; OHTA, S.
2006-01-01
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a -1 ∼ 1.7GeV and the spatial volume is about (1.9fm) 3 . Despite the small volume, the ratio of the isovector vector and axial charges g A /g V and that of structure function moments u-d / Δu-Δd are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a -1 ∼ 1.6GeV and the spatial volume is about (3.0fm) 3 . Even with preliminary statistics of 25-30 gauge configurations, the ratios g A /g V and u-d / Δu-Δd are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d 1 , though yet to be renormalized, appears small in both sets
Towards the confirmation of QCD on the lattice. Improved actions and algorithms
International Nuclear Information System (INIS)
Krieg, Stefan F.
2009-01-01
Lattice Quantum Chromodynamics has made tremendous progress over the last decade. New and improved simulation algorithms and lattice actions enable simulations of the theory with unprecedented accuracy. In the first part of this thesis, novel simulation algorithms for dynamical overlap fermions are presented. The generic Hybrid Monte Carlo algorithm is adapted to treat the singularity in the Molecular Dynamics force, to increase the tunneling rate between different topological sectors and to improve the overall volume scaling of the combined algorithm. With this new method, simulations with dynamical overlap fermions can reach smaller lattice spacings, larger volumes, smaller quark masses, and therefore higher precision than had previously been possible. The second part of this thesis is focused on a large scale simulation aiming to compute the light hadron mass spectrum. This simulation is based on a tree-level Symanzik improved gauge and tree-level improved stout-smeared Wilson clover action. The efficiency of the combination of this action and the improved simulation algorithms used allows to completely control all systematic errors. Therefore, this simulation provides a highly accurate ab initio calculation of the masses of the light hadrons, such as the proton, responsible for 95% of the mass of the visible universe, and confirms Lattice QCD in the light hadron sector. (orig.)
Towards the confirmation of QCD on the lattice. Improved actions and algorithms
Energy Technology Data Exchange (ETDEWEB)
Krieg, Stefan F.
2009-07-01
Lattice Quantum Chromodynamics has made tremendous progress over the last decade. New and improved simulation algorithms and lattice actions enable simulations of the theory with unprecedented accuracy. In the first part of this thesis, novel simulation algorithms for dynamical overlap fermions are presented. The generic Hybrid Monte Carlo algorithm is adapted to treat the singularity in the Molecular Dynamics force, to increase the tunneling rate between different topological sectors and to improve the overall volume scaling of the combined algorithm. With this new method, simulations with dynamical overlap fermions can reach smaller lattice spacings, larger volumes, smaller quark masses, and therefore higher precision than had previously been possible. The second part of this thesis is focused on a large scale simulation aiming to compute the light hadron mass spectrum. This simulation is based on a tree-level Symanzik improved gauge and tree-level improved stout-smeared Wilson clover action. The efficiency of the combination of this action and the improved simulation algorithms used allows to completely control all systematic errors. Therefore, this simulation provides a highly accurate ab initio calculation of the masses of the light hadrons, such as the proton, responsible for 95% of the mass of the visible universe, and confirms Lattice QCD in the light hadron sector. (orig.)
Hadronic matrix elements in the QCD on the lattice
International Nuclear Information System (INIS)
Altmeyer, R.
1995-01-01
The work describes a lattice simulation of full QCD with dynamical Kogut-Susskind fermions. We evaluated different hadronic matrix elements which are related to the static and low-energy behaviour of hadrons. The analysis was performed on a 16 3 x 24 lattice with a coupling constant of β = 5.35 and a quark mass of m = 0.010. The calculations are based on a set of 85 configurations created by using a Hybrid-Monte-Carlo algorithm. First we evaluated the mass and energy spectrum of the low-lying hadrons using local operators as well as non-local operators. As the complete spectrum of the different pion and ρ meson lattice representations has been calculated we were able to check the restoration of continuum flavor symmetry. Moreover, the determination of energies E of hadron states with non-vanishing momentum vector q made it possible to investigate the lattice dispersion function E( vector q). Another part of the presented work is the determination of mesonic decay constants which parameterise the weak decay of mesons. They are related to hadronic matrix elements of the respective quark currents and through the calculation of these matrix elements we were able to determine the decay constants f π and f ρ . Before doing so, we calculated non-perturbatively renormalization constants for the currents under consideration. The next part is the determination of hadronic coupling constants. These parameterise in an effective low-energy model the interactions of different hadrons. They are related to hadronic matrix elements whose lattice calculation can be dpme bu evaluating 3-point correlation functions. Thus we evaluted the hadronic coupling constants g ρππ and g NNπ . Finally, an investigation of the pion-nucleon σterm was done. The σterm is defined through a hadronic matrix element of a quark-antiquark operator and can thus be evaluated on the lattice via the calculation of a 3-point correlation function. As we determined the connected and the disconnected
Nonperturbation aspects of QCD. Monte Carlo and optimization
International Nuclear Information System (INIS)
Brezin, E.; Morel, A.; Marinari, E.; Couchot, F.; Narison, S.; Richard, J.M.; Blaizot, J.P.; Souillard, B.
1986-01-01
Phase transitions; lattice QCD; numerical simulation of lattice gauge theories; experimental research on gluonic mesons; QCD-duality sum rules; the bag model, potentials, and hadron spectra; and efficient Lagrangian functions and the Skyrme model are introduced [fr
The Contribution of Novel CP Violating Operators to the nEDM using Lattice QCD
Directory of Open Access Journals (Sweden)
Gupta Rajan
2017-01-01
Full Text Available In this talk, we motivate the calculation of the matrix elements of novel CP violating operators, the quark EDM and the quark chromo EDM operators, within the nucleon state using lattice QCD. These matrix elements, combined with the bound on the neutron EDM, would provide stringent constraints on beyond the standard model physics, especially as the next generation of neutron EDM experiments reduce the current bound. We then present our lattice strategy for the calculation of these matrix elements, in particular we describe the use of the Schrodinger source method to reduce the calculation of the 4-point to 3-point functions needed to evaluate the quark chromo EDM contribution. We end with a status report on the quality of the signal obtained in the lattice calculations of the connected contributions to the quark chromo EDM operator and the pseudoscalar operator it mixes with under renormalization.
Breakdown of the 1/N expansion in the continuum limit of strong coupling lattice QCD
International Nuclear Information System (INIS)
Bralic, N.; Pontificia Universidade Catolica de Chile, Santiago. Facultad de Fisica); Loewe, M.
1983-08-01
The restoration of lorentz covariance in the continuum limit of strong coupling lattice QCD is shown to require the breakdown of the 1/N expansion. With the leading 1/N appoximation becoming irrelevant in that limit. To leading order in 1/N lorentz convariance can be restored only as an approximate long distance symmetry a non conventional continuum limit with a non hermitian hamiltonian. (Author) [pt
Some new/old approaches to QCD
International Nuclear Information System (INIS)
Gross, D.J.
1992-11-01
In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD
Some New/Old Approaches to QCD
Gross, D. J.
1992-11-01
In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.
Some new/old approaches to QCD
Energy Technology Data Exchange (ETDEWEB)
Gross, D.J.
1992-11-01
In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.
Lattice QCD Calculations in Nuclear Physics towards the Exascale
Joo, Balint
2017-01-01
The combination of algorithmic advances and new highly parallel computing architectures are enabling lattice QCD calculations to tackle ever more complex problems in nuclear physics. In this talk I will review some computational challenges that are encountered in large scale cold nuclear physics campaigns such as those in hadron spectroscopy calculations. I will discuss progress in addressing these with algorithmic improvements such as multi-grid solvers and software for recent hardware architectures such as GPUs and Intel Xeon Phi, Knights Landing. Finally, I will highlight some current topics for research and development as we head towards the Exascale era This material is funded by the U.S. Department of Energy, Office Of Science, Offices of Nuclear Physics, High Energy Physics and Advanced Scientific Computing Research, as well as the Office of Nuclear Physics under contract DE-AC05-06OR23177.
Meson-Baryon Scattering Lengths from Mixed-Action Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Beane, S; Detmold, W; Luu, T; Orginos, K; Parreno, A; Torok, A; Walker-Loud, A
2009-06-30
The {pi}{sup +}{Sigma}{sup +}, {pi}{sup +}{Xi}{sup 0}, K{sup +}p, K{sup +}n, {bar K}{sup 0}{Sigma}{sup +}, and {bar K}{sup 0}{Xi}{sup 0} scattering lengths are calculated in mixed-action Lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations at four light-quark masses, and at two light-quark masses on the fine MILC configurations. Heavy Baryon Chiral Perturbation Theory with two and three flavors of light quarks is used to perform the chiral extrapolations. We find no convergence for the kaon-baryon processes in the three-flavor chiral expansion. Using the two-flavor chiral expansion, we find a{sub {pi}{sup +}{Sigma}{sup +}} = -0.197 {+-} 0.017 fm, and a{sub {pi}{sup +}{Xi}{sup 0}} = -0.098 {+-} 0.017 fm, where the comprehensive error includes statistical and systematic uncertainties.
Non-perturbative investigation of current correlators in twisted mass lattice QCD
International Nuclear Information System (INIS)
Petschlies, Marcus
2013-01-01
We present an investigation of hadronic current-current correlators based on the first principles of Quantum Chromodynamics. Specifically we apply the non-perturbative methods of twisted mass lattice QCD with dynamical up and down quark taking advantage of its automatic O(a) improvement. As a special application we discuss the calculation of the hadronic leading order contribution to the muon anomalous magnetic moment. The latter is regarded as a promising quantity for the search for physics beyond the standard model. The origin of the strong interest in the muon anomaly lies in the persistent discrepancy between the standard model estimate and its experimental measurement. In the theoretical determination the hadronic leading order part is currently afflicted with the largest uncertainty and a dedicated lattice investigation of the former can be of strong impact on future estimates. We discuss our study of all systematic uncertainties in the lattice calculation, including three lattice volumes, two lattice spacings, pion masses from 650 MeV to 290 MeV and the quark-disconnected contribution. We present a new method for the extrapolation to the physical point that softens the pion mass dependence of a μ hlo and allows for a linear extrapolation with small statistical uncertainty at the physical point. We determine the contribution of up and down quark as a μ hlo (N f =2)=5.69(15)10 -8 . The methods used for the muon are extended to the electron and tau lepton and we find a e hlo (N f =2)=1.512(43)10 -12 and a τ hlo (N f =2)=2.635(54)10 -6 . We estimate the charm contribution to a μ hlo in partially quenched tmLQCD with the result a μ hlo (charm)=1.447(24)(30)10 -9 in very good agreement with a dispersion-relation based result using experimental data for the hadronic R-ratio.
Finite size effects in lattice QCD with dynamical Wilson fermions
Energy Technology Data Exchange (ETDEWEB)
Orth, B.
2004-06-01
Due to limited computing resources choosing the parameters for a full lattice QCD simulation always amounts to a compromise between the competing objectives of a lattice spacing as small, quarks as light, and a volume as large as possible. Aiming at pushing unquenched simulations with the standard Wilson action towards the computationally expensive regime of small quark masses, the GRAL project addresses the question whether computing time can be saved by sticking to lattices with rather modest numbers of grid sites and extrapolating the finite-volume results to the infinite volume (prior to the usual chiral and continuum extrapolations). In this context we investigate in this work finite-size effects in simulated light hadron masses. Understanding their systematic volume dependence may not only help saving computer time in light quark simulations with the Wilson action, but also guide future simulations with dynamical chiral fermions which for a foreseeable time will be restricted to rather small lattices. We analyze data from hybrid Monte Carlo simulations with the N{sub f} = 2 Wilson action at two values of the coupling parameter, {beta} = 5.6 (lattice spacing {alpha} {approx} 0.08 fm) and {beta} = 5.32144 ({alpha} {approx} 0.13 fm). The larger {beta} corresponds to the coupling used previously by SESAM/T{chi}L. The considered hopping parameters {kappa} = 0.1575, 0.158 (at the larger {beta}) and {kappa} = 0.1665 (at the smaller {beta}) correspond to quark masses of 85, 50 and 36% of the strange quark mass, respectively. At each quark mass we study at least three different lattice extents in the range from L = 10 to L = 24 (0.85-2.04 fm). Estimates of autocorrelation times in the stochastic updating process and of the computational cost of every run are given. For each simulated sea quark mass we calculate quark propagators and hadronic correlation functions in order to extract the pion, rho and nucleon masses as well as the pion decay constant and the quark mass
Lattice regularized chiral perturbation theory
International Nuclear Information System (INIS)
Borasoy, Bugra; Lewis, Randy; Ouimet, Pierre-Philippe A.
2004-01-01
Chiral perturbation theory can be defined and regularized on a spacetime lattice. A few motivations are discussed here, and an explicit lattice Lagrangian is reviewed. A particular aspect of the connection between lattice chiral perturbation theory and lattice QCD is explored through a study of the Wess-Zumino-Witten term
QCD on the Cell Broadband Engine
Energy Technology Data Exchange (ETDEWEB)
Meyer, Nils [Department of Physics, University of Regensburg, 93040 Regensburg (Germany)
2008-07-01
We evaluate IBM's Enhanced Cell Broadband Engine (BE) as a possible building block of a new generation of lattice QCD machines. The Enhanced Cell BE will provide full support of double precision floating-point arithmetics, including IEEE-compliant rounding. We have developed a performance model and applied it to relevant lattice QCD kernels. The performance estimates are supported by micro- and application-benchmarks that have been obtained on currently available Cell BE-based computers, such as IBM QS20 blades and PlayStation 3. The results are encouraging and show that this processor is an interesting option for lattice QCD applications. For a massively parallel machine on the basis of the Cell BE, an application-optimized network needs to be developed.
QCD on the Cell Broadband Engine
Energy Technology Data Exchange (ETDEWEB)
Meyer, Nils [Department of Physics, University of Regensburg, 93040 Regensburg (Germany)
2008-07-01
We evaluate IBM's Enhanced Cell Broadband Engine (BE) as a possible building block of a new generation of lattice QCD machines. The Enhanced Cell BE will provide full support of double precision floating-point arithmetics, including IEEE-compliant rounding. We have developed a performance model and applied it to relevant lattice QCD kernels. The performance estimates are supported by micro- and application-benchmarks that have been obtained on currently available Cell BE-based computers, such as IBM QS20 blades and PlayStation 3. The results are encouraging and show that this processor is an interesting option for lattice QCD applications. For a massively parallel machine on the basis of the Cell BE, an application-optimized network needs to be developed.
Light hadron spectrum and quark masses from quenched lattice QCD
International Nuclear Information System (INIS)
Aoki, S.; Boyd, G.; Ejiri, S.; Kaneko, T.; Nagai, K.; Shanahan, H.P.; Burkhalter, R.; Iwasaki, Y.; Kanaya, K.; Ukawa, A.; Yoshie, T.; Fukugita, M.; Hashimoto, S.; Kuramashi, Y.; Okawa, M.
2003-01-01
We present the details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on lattices of size 32 3 x56-64 3 x112 at four values of lattice spacings in the range a≅0.1-0.05 fm and spatial extent L s a≅3 fm. Hadronic observables are calculated at five quark masses corresponding to m PS /m V ≅0.75-0.4, assuming the u and d quarks are degenerate, but treating the s quark separately. We find that the presence of quenched chiral singularities is supported from an analysis of the pseudoscalar meson data. The physical values of hadron masses are determined using m π , m ρ , and m K (or m φ ) as input to fix the physical scale of lattice spacing and the u, d, and s quark masses. After chiral and continuum extrapolations, the agreement of the calculated mass spectrum with experiment is at a 10% level. In comparison with the statistical accuracy of 1%-3% and systematic errors of at most 1.7% we have achieved, this demonstrates a failure of the quenched approximation for the hadron spectrum: the hyperfine splitting in the meson sector is too small, and in the baryon sector the octet masses and mass splitting of the decuplet are both smaller than experiment. Light quark masses are calculated using two definitions: the conventional one and the one based on the axial-vector Ward identity. The two results converge toward the continuum limit, yielding m ud =4.29(14) -0.79 +0.51 MeV where the first error is statistical and the second one is systematic due to chiral extrapolation. The s quark mass depends on the strange hadron mass chosen for input: m s =113.8(2.3) -2.9 +5.8 MeV from m K and m s =142.3(5.8) -0 +22.0 MeV from m φ , indicating again a failure of the quenched approximation. We obtain the scale of QCD, Λ MS (0) =219.5(5.4) MeV with m ρ used as input. An O(10%) deviation from experiment is observed in the pseudoscalar meson
Energy Technology Data Exchange (ETDEWEB)
Nube, Andreas [DESY Zeuthen, Platanenallee 6, 15738 Zeuthen (Germany)
2013-07-01
The aim of this project is to calculate a theoretical estimate of the D{sub s}-meson decay constant f{sub D{sub s}} in the framework of lattice-QCD with a chirally rotated mass term and four dynamic quark flavours (up, down, strange and charm). A comprehensive set of gauge configurations has been produced with high input on super-computers across Europe. Data from three different lattice spacings is available with four to eight different light quark masses each. HMXPT is used to extrapolate the estimates of f{sub D{sub s}} to the physical point. First determinations indicate a good agreement with both, former lattice determinations and experimental measurements.
Lattice Quantum Chromodynamics
Sachrajda, C T
2016-01-01
I review the the application of the lattice formulation of QCD and large-scale numerical simulations to the evaluation of non-perturbative hadronic effects in Standard Model Phenomenology. I present an introduction to the elements of the calculations and discuss the limitations both in the range of quantities which can be studied and in the precision of the results. I focus particularly on the extraction of the QCD parameters, i.e. the quark masses and the strong coupling constant, and on important quantities in flavour physics. Lattice QCD is playing a central role in quantifying the hadronic effects necessary for the development of precision flavour physics and its use in exploring the limits of the Standard Model and in searches for inconsistencies which would signal the presence of new physics.
International Nuclear Information System (INIS)
Hasenfratz, A.; Hasenfratz, P.
1985-01-01
This paper deals almost exclusively with applications in QCD. Presumably QCD will remain in the center of lattice calculations in the near future. The existing techniques and the available computer resources should be able to produce trustworthy results in pure SU(3) gauge theory and in quenched hadron spectroscopy. Going beyond the quenched approximation might require some technical breakthrough or exceptional computer resources, or both. Computational physics has entered high-energy physics. From this point of view, lattice QCD is only one (although the most important, at present) of the research fields. Increasing attention is devoted to the study of other QFTs. It is certain that the investigation of nonasymptotically free theories, the Higgs phenomenon, or field theories that are not perturbatively renormalizable will be important research areas in the future
Nucleon Structure and Hyperon Form Factors from Lattice QCD.
Energy Technology Data Exchange (ETDEWEB)
Lin,H.W.
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon {Sigma} and {Xi} axial coupling constants are also performed for the first time in a lattice calculation, g{sub {Sigma}{Sigma}} = 0.441(14) and g{sub {Xi}{Xi}} = -0.277(11).
Nucleon Structure and hyperon form factors from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Lin, Huey-Wen
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistant with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g_SigmaSigma = 0.441(14) and g_XiXi = -0.277(11).
Lattice calculations in gauge theory
International Nuclear Information System (INIS)
Rebbi, C.
1985-01-01
The lattice formulation of quantum gauge theories is discussed as a viable technique for quantitative studies of nonperturbative effects in QCD. Evidence is presented to ascertain that whole classes of lattice actions produce a universal continuum limit. Discrepancies between numerical results from Monto Carlo simulations for the pure gauge system and for the system with gauge and quark fields are discussed. Numerical calculations for QCD require very substantial computational resources. The use of powerful vector processors of special purpose machines, in extending the scope and magnitude or the calculations is considered, and one may reasonably expect that in the near future good quantitative predictions will be obtained for QCD
Quenched lattice QCD with domain wall fermions and the chiral limit
International Nuclear Information System (INIS)
Blum, T.; Wingate, M.; Chen, P.; Christ, N.; Cristian, C.; Fleming, G.; Kaehler, A.; Liao, X.; Liu, G.; Malureanu, C.; Mawhinney, R.; Siegert, G.; Sui, C.; Wu, L.; Zhestkov, Y.; Dawson, C.; Soni, A.; Ohta, S.; Vranas, P.
2004-01-01
Quenched QCD simulations on three volumes 8 3 x, 12 3 x and 16 3 x32 and three couplings β=5.7, 5.85 and 6.0 using domain wall fermions provide a consistent picture of quenched QCD. We demonstrate that the small induced effects of chiral symmetry breaking inherent in this formulation can be described by a residual mass (m res ) whose size decreases as the separation between the domain walls (L s ) is increased. However, at stronger couplings much larger values of L s are required to achieve a given physical value of m res . For β=6.0 and L s =16, we find m res /m s =0.033(3), while for β=5.7, and L s =48, m res /m s =0.074(5), where m s is the strange quark mass. These values are significantly smaller than those obtained from a more naive determination in our earlier studies. Important effects of topological near zero modes which should afflict an accurate quenched calculation are easily visible in both the chiral condensate and the pion propagator. These effects can be controlled by working at an appropriately large volume. A non-linear behavior of m π 2 in the limit of small quark mass suggests the presence of additional infrared subtlety in the quenched approximation. Good scaling is seen both in masses and in f π over our entire range, with inverse lattice spacing varying between 1 and 2 GeV
In-medium P-wave quarkonium from the complex lattice QCD potential
International Nuclear Information System (INIS)
Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander
2016-01-01
We extend our lattice QCD potential based study http://dx.doi.org/10.1007/JHEP12(2015)101 of the in-medium properties of heavy quark bound states to P-wave bottomonium and charmonium. Similar to the behavior found in the S-wave channel their spectra show a characteristic broadening, as well as mass shifts to lower energy with increasing temperature. In contrast to the S-wave states, finite angular momentum leads to the survival of spectral peaks even at temperatures, where the continuum threshold reaches below the bound state remnant mass. We elaborate on the ensuing challenges in defining quarkonium dissolution and present estimates of melting temperatures for the spin averaged χ b and χ c states. As an application to heavy-ion collisions we further estimate the contribution of feed down to S-wave quarkonium through the P-wave states after freezeout.
In-medium P-wave quarkonium from the complex lattice QCD potential
Energy Technology Data Exchange (ETDEWEB)
Burnier, Yannis [Institute of Theoretical Physics, EPFL,CH-1015 Lausanne (Switzerland); Kaczmarek, Olaf [Fakultät für Physik, Universität Bielefeld,D-33615 Bielefeld (Germany); Rothkopf, Alexander [Institute for Theoretical Physics, Heidelberg University,Philosophenweg 16, 69120 Heidelberg (Germany)
2016-10-07
We extend our lattice QCD potential based study http://dx.doi.org/10.1007/JHEP12(2015)101 of the in-medium properties of heavy quark bound states to P-wave bottomonium and charmonium. Similar to the behavior found in the S-wave channel their spectra show a characteristic broadening, as well as mass shifts to lower energy with increasing temperature. In contrast to the S-wave states, finite angular momentum leads to the survival of spectral peaks even at temperatures, where the continuum threshold reaches below the bound state remnant mass. We elaborate on the ensuing challenges in defining quarkonium dissolution and present estimates of melting temperatures for the spin averaged χ{sub b} and χ{sub c} states. As an application to heavy-ion collisions we further estimate the contribution of feed down to S-wave quarkonium through the P-wave states after freezeout.
Dynamical fermions in lattice quantum chromodynamics
Energy Technology Data Exchange (ETDEWEB)
Szabo, Kalman
2007-07-01
The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)
Dynamical fermions in lattice quantum chromodynamics
International Nuclear Information System (INIS)
Szabo, Kalman
2007-01-01
The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)
Absence of evidence for pentaquarks on the lattice
International Nuclear Information System (INIS)
Holland, Kieran; Juge, K. Jimmy
2006-01-01
We study the question of whether or not QCD predicts a pentaquark state Θ + . We use the improved, fixed point lattice QCD action which has very little sensitivity to the lattice spacing and also allows us to reach light quark masses. The analysis was performed on a single volume of size (1.8 fm) 3 x3.6 fm with lattice spacing of a=0.102 fm. We use the correlation matrix method to identify the ground and excited states in the isospin 0, negative parity channel. In the quenched approximation where dynamical quark effects are omitted, we do not find any evidence for a pentaquark resonance in QCD
A local factorization of the fermion determinant in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Ce, Marco [Scuola Normale Superiore, Pisa (Italy); INFN, Pisa (Italy); Giusti, Leonardo [Milano-Bicocca Univ. (Italy). Dipartimento di Fisica; INFN, Milano-Bicocca (Italy); Schaefer, Stefan [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2016-09-15
We introduce a factorization of the fermion determinant in lattice QCD with Wilson-type fermions that leads to a bosonic action which is local in the block fields. The interaction among gauge fields on distant blocks is mediated by multiboson fields located on the boundaries of the blocks. The resultant multiboson domain-decomposed hybrid Monte Carlo passes extensive numerical tests carried out by measuring standard gluonic observables. The combination of the determinant factorization and of the one of the propagator, that we put forward recently, paves the way for multilevel Monte Carlo integration in the presence of fermions. We test this possibility by computing the disconnected correlator of two flavor-diagonal pseudoscalar densities, and we observe a significant increase of the signal-to-noise ratio due to a two-level integration.
Isotensor Axial Polarizability and Lattice QCD Input for Nuclear Double- \beta Decay Phenomenology
Energy Technology Data Exchange (ETDEWEB)
Shanahan, Phiala E.; Tiburzi, Brian C.; Wagman, Michael L.; Winter, Frank; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas; Savage, Martin J.
2017-08-01
The potential importance of short-distance nuclear effects in double-$\\beta$ decay is assessed using a lattice QCD calculation of the $nn\\rightarrow pp$ transition and effective field theory methods. At the unphysical quark masses used in the numerical computation, these effects, encoded in the isotensor axial polarisability, are found to be of similar magnitude to the nuclear modification of the single axial current, which phenomenologically is the quenching of the axial charge used in nuclear many-body calculations. This finding suggests that nuclear models for neutrinoful and neutrinoless double-$\\beta$ decays should incorporate this previously neglected contribution if they are to provide reliable guidance for next-generation neutrinoless double-$\\beta$ decay searches. The prospects of constraining the isotensor axial polarisabilities of nuclei using lattice QCD input into nuclear many-body calculations are discussed.
Thermodynamics of lattice QCD with massless quarks and chiral 4-fermion interactions
International Nuclear Information System (INIS)
Kogut, J. B.
1998-01-01
N f = 2 lattice QCD with massless quarks and a weak 4-fermion interaction appears to have the expected second order transition, at least for N t ≥ 6. More work is needed to clarify the N t = 4 case. With more statistics the N t = 6 simulations should produce an accurate determination of the critical exponent β m . Moving to finite mass at β = β c should allow an accurate determination of σ. Hadronic screening masses need further analysis. Other order parameters remain to be analyzed. Unfortunately, there is no obvious way to include 4-fermion interactions with full SU(2) x SU(2) chiral flavor symmetry
Electric Dipole Moment of the Neutron from 2+1 Flavor Lattice QCD.
Guo, F-K; Horsley, R; Meissner, U-G; Nakamura, Y; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A; Zanotti, J M
2015-08-07
We compute the electric dipole moment d(n) of the neutron from a fully dynamical simulation of lattice QCD with 2+1 flavors of clover fermions and nonvanishing θ term. The latter is rotated into a pseudoscalar density in the fermionic action using the axial anomaly. To make the action real, the vacuum angle θ is taken to be purely imaginary. The physical value of dd(n) is obtained by analytic continuation. We find d(n)=-3.9(2)(9)×10(-16) θ e cm, which, when combined with the experimental limit on d(n), leads to the upper bound |θ|≲7.4×10(-11).
Kaon matrix elements and CP violation from quenched lattice QCD: The 3-flavor case
International Nuclear Information System (INIS)
Blum, T.; Wingate, M.; Chen, P.; Christ, N.; Cristian, C.; Fleming, G.; Mawhinney, R.; Siegert, G.; Wu, L.; Zhestkov, Y.; Dawson, C.; Soni, A.; Ohta, S.; Vranas, P.
2003-01-01
We report the results of a calculation of the K→ππ matrix elements relevant for the ΔI=1/2 rule and ε ' /ε in quenched lattice QCD using domain wall fermions at a fixed lattice spacing a -1 ∼2 GeV. Working in the three-quark effective theory, where only the u, d, and s quarks enter and which is known perturbatively to next-to-leading order, we calculate the lattice K→π and K→|0> matrix elements of dimension six, four-fermion operators. Through lowest order chiral perturbation theory these yield K→ππ matrix elements, which we then normalize to continuum values through a nonperturbative renormalization technique. For the ratio of isospin amplitudes vertical bar A 0 vertical bar/vertical bar A 2 vertical bar we find a value of 25.3±1.8 (statistical error only) compared to the experimental value of 22.2, with individual isospin amplitudes 10%-20% below the experimental values. For ε ' /ε, using known central values for standard model parameters, we calculate (-4.0±2.3)x10 -4 (statistical error only) compared to the current experimental average of (17.2±1.8)x10 -4 . Because we find a large cancellation between the I=0 and I=2 contributions to ε ' /ε, the result may be very sensitive to the approximations employed. Among these are the use of quenched QCD, lowest order chiral perturbation theory, and continuum perturbation theory below 1.3 GeV. We also calculate the kaon B parameter B K and find B K,MS (2 GeV)=0.532(11). Although currently unable to give a reliable systematic error, we have control over statistical errors and more simulations will yield information about the effects of the approximations on this first-principles determination of these important quantities
Athenodorou, Andreas; Boucaud, Philippe; de Soto, Feliciano; Rodríguez-Quintero, José; Zafeiropoulos, Savvas
2018-03-01
We report on an instanton-based analysis of the gluon Green functions in the Landau gauge for low momenta; in particular we use lattice results for αs in the symmetric momentum subtraction scheme (MOM) for large-volume lattice simulations. We have exploited quenched gauge field configurations, Nf = 0, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with Nf = 2 + 1 and Nf = 2 + 1 + 1 dynamical flavors (domain wall and twisted-mass fermions, respectively). We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination of phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing. We furthermore apply the Gradient Flow to remove short-distance fluctuations. The Gradient Flow gets rid of the QCD scale, ΛQCD, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of the instanton density and size distribution that is compatible with those extracted from the analysis of the Green functions.
Flavor-singlet baryons in the graded symmetry approach to partially quenched QCD
Hall, Jonathan M. M.; Leinweber, Derek B.
2016-11-01
Progress in the calculation of the electromagnetic properties of baryon excitations in lattice QCD presents new challenges in the determination of sea-quark loop contributions to matrix elements. A reliable estimation of the sea-quark loop contributions represents a pressing issue in the accurate comparison of lattice QCD results with experiment. In this article, an extension of the graded symmetry approach to partially quenched QCD is presented, which builds on previous theory by explicitly including flavor-singlet baryons in its construction. The formalism takes into account the interactions among both octet and singlet baryons, octet mesons, and their ghost counterparts; the latter enables the isolation of the quark-flow disconnected sea-quark loop contributions. The introduction of flavor-singlet states enables systematic studies of the internal structure of Λ -baryon excitations in lattice QCD, including the topical Λ (1405 ).
Morningstar, C; Fahy, B; Foley, J; Jhang, Y C; Juge, K J; Lenkner, D; Wong, C C H
2013-01-01
Multi-hadron operators are crucial for reliably extracting the masses of excited states lying above multi-hadron thresholds in lattice QCD Monte Carlo calculations. The construction of multi-hadron operators with significant coupling to the lowest-lying states of interest involves combining single hadron operators of various momenta. The design and implementation of large sets of spatially-extended single-hadron operators of definite momentum and their combinations into two-hadron operators are described. The single hadron operators are all assemblages of gauge-covariantly-displaced, smeared quark fields. Group-theoretical projections onto the irreducible representations of the symmetry group of a cubic spatial lattice are used in all isospin channels. Tests of these operators on 24^3 x 128 and 32^3 x 256 anisotropic lattices using a stochastic method of treating the low-lying modes of quark propagation which exploits Laplacian Heaviside quark-field smearing are presented. The method provides reliable estimat...
Transverse momentum-dependent parton distribution functions in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, Michael G. [New Mexico State University; Musch, Bernhard U. [Tech. University Munich; Haegler, Philipp G. [Tech. University Munich; Negele, John W. [MIT; Schaefer, Andreas [Regensburg
2013-08-01
A fundamental structural property of the nucleon is the distribution of quark momenta, both parallel as well as perpendicular to its propagation. Experimentally, this information is accessible via selected processes such as semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY), which can be parametrized in terms of transversemomentum-dependent parton distributions (TMDs). On the other hand, these distribution functions can be extracted from nucleon matrix elements of a certain class of bilocal quark operators in which the quarks are connected by a staple-shaped Wilson line serving to incorporate initial state (DY) or final state (SIDIS) interactions. A scheme for evaluating such matrix elements within lattice QCD is developed. This requires casting the calculation in a particular Lorentz frame, which is facilitated by a parametrization of the matrix elements in terms of invariant amplitudes. Exploratory results are presented for the time-reversal odd Sivers and Boer-Mulders transverse momentum shifts.
Tetraquark operators in lattice QCD and exotic flavour states in the charm sector
Cheung, Gavin K. C.; Thomas, Christopher E.; Dudek, Jozef J.; Edwards, Robert G.
2017-11-01
We present a general class of operators resembling compact tetraquarks which have a range of colour-flavour-spin structures, transform irreducibly under the symmetries of the lattice and respect other relevant symmetries. These constructions are demonstrated in lattice QCD calculations with light quarks corresponding to m π = 391 MeV. Using the distillation framework, correlation functions involving large bases of meson-meson and tetraquark operators are computed in the isospin-1 hidden-charm and doubly-charmed sectors, and finite-volume spectra are extracted with the variational method. We find the spectra are insensitive to the addition of tetraquark operators to the bases of meson-meson operators. For the first time, through using diverse bases of meson-meson operators, the multiple energy levels associated with meson-meson levels which would be degenerate in the non-interacting limit are extracted reliably. The number of energy levels in each spectrum is found to be equal to the number of expected non-interacting meson-meson levels in the energy region considered and the majority of energies lie close to the non-interacting levels. Therefore, there is no strong indication for any bound state or narrow resonance in the channels we study.
Large scale simulations of lattice QCD thermodynamics on Columbia Parallel Supercomputers
International Nuclear Information System (INIS)
Ohta, Shigemi
1989-01-01
The Columbia Parallel Supercomputer project aims at the construction of a parallel processing, multi-gigaflop computer optimized for numerical simulations of lattice QCD. The project has three stages; 16-node, 1/4GF machine completed in April 1985, 64-node, 1GF machine completed in August 1987, and 256-node, 16GF machine now under construction. The machines all share a common architecture; a two dimensional torus formed from a rectangular array of N 1 x N 2 independent and identical processors. A processor is capable of operating in a multi-instruction multi-data mode, except for periods of synchronous interprocessor communication with its four nearest neighbors. Here the thermodynamics simulations on the two working machines are reported. (orig./HSI)
Results for the η' mass from two-flavour lattice QCD
International Nuclear Information System (INIS)
Lesk, V.I.; Aoki, S.; Burkhalter, R.; Fukugita, M.; Ishikawa, K.I.; Ishizuka, N.; Iwasaki, Y.; Kanay, K.; Kaneko, T.; Kuramashi, Y.; Okawa, M.; Taniguchi, Y.; Ukawa, A.; Umeda, T.; Yoshie, T.
2003-01-01
We present results for the mass of the η' meson for two-flavor lattice QCD in the continuum limit, calculated on the CP-PACS computer, using an RG-improved gauge action and clover fermion action with tadpole-improved c sw . Measurements are made at three couplings corresponding to a ∼ 0.22, 0.16, 0.11 fm for four quark masses corresponding to m π /m ρ ∼ 0.8, 0.75, 0.7, 0.6. The two-loop diagrams are evaluated using a noisy source method. Quark smearing for both one- and two- loop diagrams is successfully applied to obtain ground state signals in the η' channel. We obtain m η' =0.960(87) -0.286 +0.036 in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations
The strange and light quark contributions to the nucleon mass from lattice QCD
International Nuclear Information System (INIS)
Bali, Gunnar S.; Collins, Sara; Goeckeler, Meinulf
2011-12-01
We determine the strangeness and light quark fractions of the nucleon mass by computing the quark line connected and disconnected contributions to the matrix elements m q left angle N vertical stroke anti qq vertical stroke N right angle in lattice QCD, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson Fermionic action. We simulate n F =2 mass degenerate sea quarks with a pion mass of about 285 MeV and a lattice spacing ∼0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon σ-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized values σ πN =(38±12) MeV at the physical point and f T s =σ s /m N =0.012(14) +10 -3 for the strangeness contribution at our larger than physical sea quark mass. (orig.)
The strange and light quark contributions to the nucleon mass from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Bali, Gunnar S.; Collins, Sara; Goeckeler, Meinulf [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)
2011-12-15
We determine the strangeness and light quark fractions of the nucleon mass by computing the quark line connected and disconnected contributions to the matrix elements m{sub q} left angle N vertical stroke anti qq vertical stroke N right angle in lattice QCD, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson Fermionic action. We simulate n{sub F}=2 mass degenerate sea quarks with a pion mass of about 285 MeV and a lattice spacing {approx}0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon {sigma}-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized values {sigma}{sub {pi}}{sub N}=(38{+-}12) MeV at the physical point and f{sub T{sub s}}={sigma}{sub s}/m{sub N}=0.012(14){sup +10}{sub -3} for the strangeness contribution at our larger than physical sea quark mass. (orig.)
Improved stochastic estimation of quark propagation with Laplacian Heaviside smearing in lattice QCD
International Nuclear Information System (INIS)
Morningstar, C.; Lenkner, D.; Wong, C.H.; Bulava, J.; Foley, J.; Juge, K.J.; Peardon, M.
2011-08-01
A new method of stochastically estimating the low-lying effects of quark propagation is proposed which allows accurate determinations of temporal correlations of single-hadron and multi-hadron operators in lattice QCD. The method is well suited for calculations in large volumes. Contributions involving quark propagation connecting hadron sink operators at the same final time can be handled in a straightforward manner, even for a large number of final time slices. The method exploits Laplacian Heaviside (LapH) smearing. Z N noise is introduced in a novel way, and variance reduction is achieved using judiciously-chosen noise dilution projectors. The method is tested using isoscalar mesons in the scalar, pseudoscalar, and vector channels, and using the two-pion system of total isospin I=0,1,2 on large anisotropic 24 3 x 128 lattices with spatial spacing a s ∝0.12 fm and temporal spacing a t ∝0.034 fm for pion masses m π ∼ 390 and 240 MeV. (orig.)
Nonperturbative QCD simulations with 2+1 flavors of improved staggered quarks
International Nuclear Information System (INIS)
Bazavov, A.; Toussaint, D.; Bernard, C.; Laiho, J.; DeTar, C.; Levkova, L.; Oktay, M. B.; Gottlieb, Steven; Heller, U. M.; Hetrick, J. E.; Mackenzie, P. B.; Sugar, R.; Van de Water, R. S.
2010-01-01
Dramatic progress has been made over the last decade in the numerical study of quantum chromodynamics (QCD) through the use of improved formulations of QCD on the lattice (improved actions), the development of new algorithms, and the rapid increase in computing power available to lattice gauge theorists. In this article simulations of full QCD are described using the improved staggered quark formalism, ''asqtad'' fermions. These simulations were carried out with two degenerate flavors of light quarks (up and down) and with one heavier flavor, the strange quark. Several light quark masses, down to about three times the physical light quark mass, and six lattice spacings have been used. These enable controlled continuum and chiral extrapolations of many low energy QCD observables. The improved staggered formalism is reviewed, emphasizing both advantages and drawbacks. In particular, the procedure for removing unwanted staggered species in the continuum limit is reviewed. Then the asqtad lattice ensembles created by the MILC Collaboration are described. All MILC lattice ensembles are publicly available, and they have been used extensively by a number of lattice gauge theory groups. The physics results obtained with them are reviewed, and the impact of these results on phenomenology is discussed. Topics include the heavy quark potential, spectrum of light hadrons, quark masses, decay constants of light and heavy-light pseudoscalar mesons, semileptonic form factors, nucleon structure, scattering lengths, and more.
Numerical studies of QCD renormalons in high-order perturbative expansions
International Nuclear Information System (INIS)
Bauer, Clemens
2013-01-01
Perturbative expansions in four-dimensional non-Abelian gauge theories such as Quantum Chromodynamics (QCD) are expected to be divergent, at best asymptotic. One reason is that it is impossible to strictly exclude from the relevant Feynman diagrams those energy regions in which a perturbative treatment is inapplicable. The divergent nature of the series is then signaled by a rapid (factorial) growth of the perturbative expansion coefficients, commonly referred to as a renormalon. In QCD, the most severe divergences occur in the infrared (IR) limit and therefore they are classified as IR renormalons. Their appearance can be understood within the well-accepted Operator Product Expansion (OPE) framework. According to the OPE, the perturbative calculation of a physical observable must be amended by non-perturbative power corrections that come in the form of condensates, universal characteristics of the rich QCD vacuum structure. Adding up perturbative and non-perturbative contributions, the ambiguity due to the renormalon cancels and the physical observable is well-defined. Although the field has made considerable progress in the last twenty years, a proof of renormalon existence is still pending. It has only been tested assuming strong simplifications or in toy models. The aim of this thesis is to provide the first numerical evidence for renormalon existence in the gauge sector of QCD. We use Numerical Stochastic Perturbation Theory (NSPT) to directly obtain perturbative coefficients within lattice regularization, a means to replace continuum spacetime by a four-dimensional hypercubic lattice. A peculiar feature of NSPT are comparatively low simulation costs when reaching high expansion orders. We examine two distinct observables: the static self-energy of an isolated quark and the elementary plaquette. Following the OPE classification, the static quark self-energy is ideally suited for a renormalon study. Taking into account peculiarities of the lattice approach such
QCD as a topologically ordered system
International Nuclear Information System (INIS)
Zhitnitsky, Ariel R.
2013-01-01
We argue that QCD belongs to a topologically ordered phase similar to many well-known condensed matter systems with a gap such as topological insulators or superconductors. Our arguments are based on an analysis of the so-called “deformed QCD” which is a weakly coupled gauge theory, but nevertheless preserves all the crucial elements of strongly interacting QCD, including confinement, nontrivial θ dependence, degeneracy of the topological sectors, etc. Specifically, we construct the so-called topological “BF” action which reproduces the well known infrared features of the theory such as non-dispersive contribution to the topological susceptibility which cannot be associated with any propagating degrees of freedom. Furthermore, we interpret the well known resolution of the celebrated U(1) A problem where the would be η ′ Goldstone boson generates its mass as a result of mixing of the Goldstone field with a topological auxiliary field characterizing the system. We then identify the non-propagating auxiliary topological field of the BF formulation in deformed QCD with the Veneziano ghost (which plays the crucial role in resolution of the U(1) A problem). Finally, we elaborate on relation between “string-net” condensation in topologically ordered condensed matter systems and long range coherent configurations, the “skeletons”, studied in QCD lattice simulations. -- Highlights: •QCD may belong to a topologically ordered phase similar to condensed matter (CM) systems. •We identify the non-propagating topological field in deformed QCD with the Veneziano ghost. •Relation between “string-net” condensates in CM systems and the “skeletons” in QCD lattice simulations is studied
Overview of lattice gauge theory at the CSSM
International Nuclear Information System (INIS)
Williams, A.G.
2002-01-01
Full text: I present an overview of the lattice gauge theory effort at the Special Research Centre for the Subatomic Structure of Matter (CSSM). The CSSM specializes in research into the strong interactions and into quantum chromodynamics (QCD), which is the fundamental quantum gauge field theory of the strong interactions. The primary mission of the CSSM is to attempt to solve QCD and hence test the implications of the theory against experimental evidence. The difficulty lies in the fact that the QCD is a highly nonlinear, strongly coupled theory. The only known first-principles means to solve it is to approximate space-time by a four-dimensional 'grid' or 'lattice' and to simulate this 'lattice QCD' on massively parallel supercomputers. A discussion of the Orion supercomputer of the National Computing Facility for Lattice Gauge Theory (NFCLGT) and the latest QCD predictions obtained from Orion by CSSM researchers will be presented
Aspects of thermodynamics and confinement in the lattice formulation of QCD
International Nuclear Information System (INIS)
Liptak, L.
2009-01-01
This dissertation thesis covers selected problems related to two aspects of the theory of strong interactions, quantum chromodynamics: thermodynamics of QCD and color confinement. The problems were treated in a nonperturbative way, in the lattice formulation of the theory. Main results of our investigation can be summarized in the following way: - Our first study was focused on properties of thermodynamical quantities for free massless fermions at non-zero temperature and chemical potential on a lattice. We used the so-called overlap Dirac operator and introduced the chemical potential in a way proposed recently by Bloch and Wettig, based on analytic continuation of the usual sign function in the complex plane. The overlap Dirac operator satisfies the proper lattice chiral symmetry defined by the Ginsparg-Wilson relation, and therefore represents an appropriate formulation for massless fermions. We analyzed the behavior of the free-fermion energy density and the number operator at non-zero chemical potential. We found that the expected behavior of these quantities in the continuum limit was reliably approached both at zero and non-zero temperatures. The conclusion is that overlap fermions with the suggested analytic continuation provide both chiral symmetry and the correct description of fermions at finite density, at least for free fermions. We also showed that the overlap fermions have a quantitatively similar behavior like Wilson fermions. - Further we studied the canonical formalism of thermodynamics. An important aspect which motivates a study of canonical partition functions is the possibility to reproduce the grand canonical partition function from canonical ones via the fugacity expansion; in this way, one can circumvent the fermion sign problem. Recently, a factorization formula of the fermion determinant was proposed by Danzer and Gattringer, which is based on the proper division of the lattice and redefinition of the chemical potential. We investigated
The Nucleon Axial Form Factor and Staggered Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Meyer, Aaron Scott [Chicago U.
2017-01-01
The study of neutrino oscillation physics is a major research goal of the worldwide particle physics program over the upcoming decade. Many new experiments are being built to study the properties of neutrinos and to answer questions about the phenomenon of neutrino oscillation. These experiments need precise theoretical cross sections in order to access fundamental neutrino properties. Neutrino oscillation experiments often use large atomic nuclei as scattering targets, which are challenging for theorists to model. Nuclear models rely on free-nucleon amplitudes as inputs. These amplitudes are constrained by scattering experiments with large nuclear targets that rely on the very same nuclear models. The work in this dissertation is the rst step of a new initiative to isolate and compute elementary amplitudes with theoretical calculations to support the neutrino oscillation experimental program. Here, the eort focuses on computing the axial form factor, which is the largest contributor of systematic error in the primary signal measurement process for neutrino oscillation studies, quasielastic scattering. Two approaches are taken. First, neutrino scattering data on a deuterium target are reanalyzed with a model-independent parametrization of the axial form factor to quantify the present uncertainty in the free-nucleon amplitudes. The uncertainties on the free-nucleon cross section are found to be underestimated by about an order of magnitude compared to the ubiquitous dipole model parametrization. The second approach uses lattice QCD to perform a rst-principles computation of the nucleon axial form factor. The Highly Improved Staggered Quark (HISQ) action is employed for both valence and sea quarks. The results presented in this dissertation are computed at physical pion mass for one lattice spacing. This work presents a computation of the axial form factor at zero momentum transfer, and forms the basis for a computation of the axial form factor momentum dependence
DEFF Research Database (Denmark)
Andersen, Christian Walther; Bulava, John; Hörz, Ben
2018-01-01
We present the first direct determination of meson-baryon resonance parameters from a scattering amplitude calculated using lattice QCD. In particular, we calculate the elastic I=3/2, p-wave nucleon-pion amplitude on a single ensemble of Nf=2+1 Wilson-clover fermions with mπ=280 MeV and mK=460 Me......V. At these quark masses, the Δ(1232) resonance pole is found close to the N-π threshold and a Breit-Wigner fit to the amplitude gives gΔNπBW=19.0(4.7) in agreement with phenomenological determinations.......We present the first direct determination of meson-baryon resonance parameters from a scattering amplitude calculated using lattice QCD. In particular, we calculate the elastic I=3/2, p-wave nucleon-pion amplitude on a single ensemble of Nf=2+1 Wilson-clover fermions with mπ=280 MeV and mK=460 Me...
Numerical Study of the Ghost-Ghost-Gluon Vertex on the Lattice
International Nuclear Information System (INIS)
Mihara, A.; Cucchieri, A.; Mendes, T.
2004-01-01
It is well known that, in Landau gauge, the renormalization function of the ghost-ghost-gluon vertex Z-tilde1 (p2) is finite and constant, at least to all orders of perturbation theory. On the other hand, a direct non-perturbative verification of this result using numerical simulations of lattice QCD is still missing. Here we present a preliminary numerical study of the ghost-ghost-gluon vertex and of its corresponding renormalization function using Monte Carlo simulations in SU(2) lattice Landau gauge. Data were obtained in 4 dimensions for lattice couplings β = 2.2, 2.3, 2.4 and lattice sides N = 4, 8, 16
Numerical study of the ghost-ghost-gluon vertex on the lattice
International Nuclear Information System (INIS)
Mihara, A.; Cucchieri, A.; Mendes, T.
2004-01-01
It is well known that, in Landau gauge, the renormalization function of the ghost-ghost-gluon vertex Z∼ 1 1(p 2 ) is finite and constant, at least to all orders of perturbation theory. On the other hand, a direct non-perturbative verification of this result using numerical simulations of lattice QCD is still missing. Here we present a preliminary numerical study of the ghost-ghost-gluon vertex and of its corresponding renormalization function using Monte Carlo simulations in SU(2) lattice Landau gauge. Data were obtained in 4 dimensions for lattice couplings β= 2.2, 2.3, 2.4 and lattice sides N = 4, 8, 16. (author)
Moments of nucleon's parton distribution for the sea and valence quarks from lattice QCD
International Nuclear Information System (INIS)
Deka, M.; Doi, T.; Dong, S. J.; Draper, T.; Liu, K. F.; Streuer, T.; Mathur, N.; Thomas, A. W.
2009-01-01
We extend the study of lowest moments, and 2 >, of the parton distribution function of the nucleon to include those of the sea quarks; this entails a disconnected insertion calculation in lattice QCD. This is carried out on a 16 3 x24 quenched lattice with Wilson fermion. The quark loops are calculated with Z 2 noise vectors and unbiased subtractions, and multiple nucleon sources are employed to reduce the statistical errors. We obtain 5σ signals for for the u, d, and s quarks, but 2 > is consistent with zero within errors. We provide results for both the connected and disconnected insertions. The perturbatively renormalized for the strange quark at μ=2 GeV is s+s =0.027±0.006 which is consistent with the experimental result. The ratio of for s vs u/d in the disconnected insertion with quark loops is calculated to be 0.88±0.07. This is about twice as large as the phenomenologically fitted ( s+s / u + d ) from experiments where u and d include both the connected and disconnected insertion parts. We discuss the source and implication of this difference.
National Computational Infrastructure for Lattice Gauge Theory
Energy Technology Data Exchange (ETDEWEB)
Brower, Richard C.
2014-04-15
SciDAC-2 Project The Secret Life of Quarks: National Computational Infrastructure for Lattice Gauge Theory, from March 15, 2011 through March 14, 2012. The objective of this project is to construct the software needed to study quantum chromodynamics (QCD), the theory of the strong interactions of sub-atomic physics, and other strongly coupled gauge field theories anticipated to be of importance in the energy regime made accessible by the Large Hadron Collider (LHC). It builds upon the successful efforts of the SciDAC-1 project National Computational Infrastructure for Lattice Gauge Theory, in which a QCD Applications Programming Interface (QCD API) was developed that enables lattice gauge theorists to make effective use of a wide variety of massively parallel computers. This project serves the entire USQCD Collaboration, which consists of nearly all the high energy and nuclear physicists in the United States engaged in the numerical study of QCD and related strongly interacting quantum field theories. All software developed in it is publicly available, and can be downloaded from a link on the USQCD Collaboration web site, or directly from the github repositories with entrance linke http://usqcd-software.github.io
Lattice QCD at the physical point meets S U (2 ) chiral perturbation theory
Dürr, Stephan; Fodor, Zoltán; Hoelbling, Christian; Krieg, Stefan; Kurth, Thorsten; Lellouch, Laurent; Lippert, Thomas; Malak, Rehan; Métivet, Thibaut; Portelli, Antonin; Sastre, Alfonso; Szabó, Kálmán; Budapest-Marseille-Wuppertal Collaboration
2014-12-01
We perform a detailed, fully correlated study of the chiral behavior of the pion mass and decay constant, based on 2 +1 flavor lattice QCD simulations. These calculations are implemented using tree-level, O (a )-improved Wilson fermions, at four values of the lattice spacing down to 0.054 fm and all the way down to below the physical value of the pion mass. They allow a sharp comparison with the predictions of S U (2 ) chiral perturbation theory (χ PT ) and a determination of some of its low energy constants. In particular, we systematically explore the range of applicability of next-to-leading order (NLO) S U (2 ) χ PT in two different expansions: the first in quark mass (x expansion), and the second in pion mass (ξ expansion). We find that these expansions begin showing signs of failure for Mπ≳300 MeV , for the typical percent-level precision of our Nf=2 +1 lattice results. We further determine the LO low energy constants (LECs), F =88.0 ±1.3 ±0.2 and BMS ¯(2 GeV )=2.61 (6 )(1 ) GeV , and the related quark condensate, ΣMS ¯(2 GeV )=(272 ±4 ±1 MeV )3 , as well as the NLO ones, ℓ¯3=2.6 (5 )(3 ) and ℓ¯4=3.7 (4 )(2 ), with fully controlled uncertainties. We also explore the next-to-next-to-leading order (NNLO) expansions and the values of NNLO LECs. In addition, we show that the lattice results favor the presence of chiral logarithms. We further demonstrate how the absence of lattice results with pion masses below 200 MeV can lead to misleading results and conclusions. Our calculations allow a fully controlled, ab initio determination of the pion decay constant with a total 1% error, which is in excellent agreement with experiment.
International Nuclear Information System (INIS)
Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G
2007-01-01
The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results
Continuing progress on a lattice QCD software infrastructure
International Nuclear Information System (INIS)
Joo, B
2008-01-01
We report on the progress of the software effort in the QCD application area of SciDAC. In particular, we discuss how the software developed under SciDAC enabled the aggressive exploitation of leadership computers, and we report on progress in the area of QCD software for multi-core architectures
A Precise determination of B(K) in quenched QCD
Dimopoulos, P.; Palombi, F.; Pena, C.; Sint, S.; Vladikas, A.
2006-01-01
The $B_K$ parameter is computed in quenched lattice QCD with Wilson twisted mass fermions. Two variants of tmQCD are used; in both of them the relevant $\\Delta S = 2$ four-fermion operator is renormalised multiplicatively. The renormalisation adopted is non-perturbative, with a Schroedinger functional renormalisation condition. Renormalisation group running is also non-perturbative, up to very high energy scales. In one of the two tmQCD frameworks the computations have been performed at the physical $K$-meson mass, thus eliminating the need of mass extrapolations. Simulations have been performed at several lattice spacings and the continuum limit was reached by combining results from both tmQCD regularisations. Finite volume effects have been partially checked and turned out to be small. Exploratory studies have also been performed with non-degenerate valence flavours. The final result for the RGI bag parameter, with all sources of uncertainty (except quenching) under control, is $\\hat B_K =0.789 \\pm 0.046$.
National Computational Infrastructure for Lattice Gauge Theory: Final Report
International Nuclear Information System (INIS)
Richard Brower; Norman Christ; Michael Creutz; Paul Mackenzie; John Negele; Claudio Rebbi; David Richards; Stephen Sharpe; Robert Sugar
2006-01-01
This is the final report of Department of Energy SciDAC Grant ''National Computational Infrastructure for Lattice Gauge Theory''. It describes the software developed under this grant, which enables the effective use of a wide variety of supercomputers for the study of lattice quantum chromodynamics (lattice QCD). It also describes the research on and development of commodity clusters optimized for the study of QCD. Finally, it provides some high lights of research enabled by the infrastructure created under this grant, as well as a full list of the papers resulting from research that made use of this infrastructure
Improved stochastic estimation of quark propagation with Laplacian Heaviside smearing in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Morningstar, C.; Lenkner, D.; Wong, C.H. [Pittsburgh Univ., PA (United States). Dept. of Physics; Bulava, J. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Foley, J. [Utah Univ., Salt Lake City, UT (United States). Dept. of Physics and Astronomy; Juge, K.J. [University of the Pacific, Stockton, CA (United States). Dept. of Physics; Peardon, M. [Trinity College, Dublin (Ireland). School of Mathematics
2011-08-15
A new method of stochastically estimating the low-lying effects of quark propagation is proposed which allows accurate determinations of temporal correlations of single-hadron and multi-hadron operators in lattice QCD. The method is well suited for calculations in large volumes. Contributions involving quark propagation connecting hadron sink operators at the same final time can be handled in a straightforward manner, even for a large number of final time slices. The method exploits Laplacian Heaviside (LapH) smearing. Z{sub N} noise is introduced in a novel way, and variance reduction is achieved using judiciously-chosen noise dilution projectors. The method is tested using isoscalar mesons in the scalar, pseudoscalar, and vector channels, and using the two-pion system of total isospin I=0,1,2 on large anisotropic 24{sup 3} x 128 lattices with spatial spacing a{sub s} {proportional_to}0.12 fm and temporal spacing a{sub t} {proportional_to}0.034 fm for pion masses m{sub {pi}} {approx} 390 and 240 MeV. (orig.)
Extension of the HAL QCD approach to inelastic and multi-particle scatterings in lattice QCD
Aoki, S.
We extend the HAL QCD approach, with which potentials between two hadrons can be obtained in QCD at energy below inelastic thresholds, to inelastic and multi-particle scatterings. We first derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than 2 particles, in terms of the one-shell $T$-matrix consrainted by the unitarity of quantum field theories. We show that its asymptotic behavior contains phase shifts and mixing angles of $n$ particle scatterings. This property is one of the essential ingredients of the HAL QCD scheme to define "potential" from the NBS wave function in quantum field theories such as QCD. We next construct energy independent but non-local potentials above inelastic thresholds, in terms of these NBS wave functions. We demonstrate an existence of energy-independent coupled channel potentials with a non-relativistic approximation, where momenta of all particles are small compared with their own masses. Combining these two results, we can employ the HAL QCD approach also to investigate inelastic and multi-particle scatterings.
The electric dipole moment of the neutron from 2+1 flavor lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Guo, F.K. [Bonn Univ. (Germany). Helmholtz Inst. fuer Strahlen- und Kernphysik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Meissner, U.G. [Bonn Univ. (Germany). Helmholtz Inst. fuer Strahlen- und Kernphysik; Forschungszentrum Juelich GmbH (Germany). Inst. for Advanced Simulation; Forschungszentrum Juelich GmbH (Germany). Inst. fuer Kernphysik; Forschungszentrum Juelich (Germany). Center for Hadron Physics; Juelich Aachen Research Alliance (Germany). JARA-FAME and JARA-HPC; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe (Japan); Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zanotti, J.M. [Adelaide Univ. (Australia). CSSM, Dept. of Physics
2015-02-15
We compute the electric dipole moment d{sub n} of the neutron from a fully dynamical simulation of lattice QCD with 2+1 flavors of clover fermions and nonvanishing theta term. The latter is rotated into the pseudoscalar density in the fermionic action using the axial anomaly. To make the action real, the vacuum angle θ is taken to be purely imaginary. The physical value of d{sub n} is obtained by analytic continuation. We find d{sub n}=-3.8(2)(9) x 10{sup -16} θ e cm, which, when combined with the experimental limit on d{sub n}, leads to the upper bound vertical stroke θ vertical stroke
Lattice NRQCD study on in-medium bottomonium spectra using a novel Bayesian reconstruction approach
International Nuclear Information System (INIS)
Kim, Seyong; Petreczky, Peter; Rothkopf, Alexander
2016-01-01
We present recent results on the in-medium modification of S- and P-wave bottomonium states around the deconfinement transition. Our study uses lattice QCD with N f = 2 + 1 light quark flavors to describe the non-perturbative thermal QCD medium between 140MeV < T < 249MeV and deploys lattice regularized non-relativistic QCD (NRQCD) effective field theory to capture the physics of heavy quark bound states immersed therein. The spectral functions of the 3 S 1 (ϒ) and 3 P 1 (χ b1 ) bottomonium states are extracted from Euclidean time Monte Carlo simulations using a novel Bayesian prescription, which provides higher accuracy than the Maximum Entropy Method. Based on a systematic comparison of interacting and free spectral functions we conclude that the ground states of both the S-wave (ϒ) and P-wave (χ b1 ) channel survive up to T = 249MeV. Stringent upper limits on the size of the in-medium modification of bottomonium masses and widths are provided
Energy Technology Data Exchange (ETDEWEB)
Athenodorou, Andreas [Cyprus Institute, Nicosia, Cyprus; Boucaud, Philippe [Univ. Paris-Sud, Orsay (France); de Soto, Feliciano [Univ. Pablo de Olavide, 41013 Sevilla; Spain; Univ. of Granada (Spain); Rodriguez-Quintero, Jose [Universidad de Huelva, 21071 Huelva; Spain; Univ. of Granada (Spain); Zafeiropoulos, Savvas [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Heidelberg Univ. (Germany). Inst. for Theoretische Physik
2018-04-01
We report on an instanton-based analysis of the gluon Green functions in the Landau gauge for low momenta; in particular we use lattice results for αs in the symmetric momentum subtraction scheme (MOM) for large-volume lattice simulations. We have exploited quenched gauge field configurations, Nf = 0, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with Nf = 2 + 1 and Nf = 2 + 1 + 1 dynamical flavors (domain wall and twisted-mass fermions, respectively).We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination of phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing.We furthermore apply the Gradient Flow to remove short-distance fluctuations. The Gradient Flow gets rid of the QCD scale, ΛQCD, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of the instanton density and size distribution that is compatible with those extracted from the analysis of the Green functions.
Introduction to finite temperature and finite density QCD
International Nuclear Information System (INIS)
Kitazawa, Masakiyo
2014-01-01
It has been pointed out that QCD (Quantum Chromodynamics) in the circumstances of medium at finite temperature and density shows numbers of phenomena similar to the characteristics of solid state physics, e.g. phase transitions. In the past ten years, the very high temperature and density matter came to be observed experimentally at the heavy ion collisions. At the same time, the numerical QCD analysis at finite temperature and density attained quantitative level analysis possible owing to the remarkable progress of computers. In this summer school lecture, it has been set out to give not only the recent results, but also the spontaneous breaking of the chiral symmetry, the fundamental theory of finite temperature and further expositions as in the following four sections. The first section is titled as 'Introduction to Finite Temperature and Density QCD' with subsections of 1.1 standard model and QCD, 1.2 phase transition and phase structure of QCD, 1.3 lattice QCD and thermodynamic quantity, 1.4 heavy ion collision experiments, and 1.5 neutron stars. The second one is 'Equilibrium State' with subsections of 2.1 chiral symmetry, 2.2 vacuum state: BCS theory, 2.3 NJL (Nambu-Jona-Lasinio) model, and 2.4 color superconductivity. The third one is 'Static fluctuations' with subsections of 3.1 fluctuations, 3.2 moment and cumulant, 3.3 increase of fluctuations at critical points, 3.4 analysis of fluctuations by lattice QCD and Taylor expansion, and 3.5 experimental exploration of QCD phase structure. The fourth one is 'Dynamical Structure' with 4.1 linear response theory, 4.2 spectral functions, 4.3 Matsubara function, and 4.4 analyses of dynamical structure by lattice QCD. (S. Funahashi)
Fundamental parameters of QCD from non-perturbative methods for two and four flavors
International Nuclear Information System (INIS)
Marinkovic, Marina
2013-01-01
The non-perturbative formulation of Quantumchromodynamics (QCD) on a four dimensional space-time Euclidean lattice together with the finite size techniques enable us to perform the renormalization of the QCD parameters non-perturbatively. In order to obtain precise predictions from lattice QCD, one needs to include the dynamical fermions into lattice QCD simulations. We consider QCD with two and four mass degenerate flavors of O(a) improved Wilson quarks. In this thesis, we improve the existing determinations of the fundamental parameters of two and four flavor QCD. In four flavor theory, we compute the precise value of the Λ parameter in the units of the scale L max defined in the hadronic regime. We also give the precise determination of the Schroedinger functional running coupling in four flavour theory and compare it to the perturbative results. The Monte Carlo simulations of lattice QCD within the Schroedinger Functional framework were performed with a platform independent program package Schroedinger Funktional Mass Preconditioned Hybrid Monte Carlo (SF-MP-HMC), developed as a part of this project. Finally, we compute the strange quark mass and the Λ parameter in two flavour theory, performing a well-controlled continuum limit and chiral extrapolation. To achieve this, we developed a universal program package for simulating two flavours of Wilson fermions, Mass Preconditioned Hybrid Monte Carlo (MP-HMC), which we used to run large scale simulations on small lattice spacings and on pion masses close to the physical value.
Statistical mechanics view of quantum chromodynamics: Lattice gauge theory
International Nuclear Information System (INIS)
Kogut, J.B.
1984-01-01
Recent developments in lattice gauge theory are discussed from a statistial mechanics viewpoint. The basic physics problems of quantum chromodynamics (QCD) are reviewed for an audience of critical phenomena theorists. The idea of local gauge symmetry and color, the connection between statistical mechanics and field theory, asymptotic freedom and the continuum limit of lattice gauge theories, and the order parameters (confinement and chiral symmetry) of QCD are reviewed. Then recent developments in the field are discussed. These include the proof of confinement in the lattice theory, numerical evidence for confinement in the continuum limit of lattice gauge theory, and perturbative improvement programs for lattice actions. Next, we turn to the new challenges facing the subject. These include the need for a better understanding of the lattice Dirac equation and recent progress in the development of numerical methods for fermions (the pseudofermion stochastic algorithm and the microcanonical, molecular dynamics equation of motion approach). Finally, some of the applications of lattice gauge theory to QCD spectrum calculations and the thermodynamics of QCD will be discussed and a few remarks concerning future directions of the field will be made
Elimination of spurious lattice fermion solutions and noncompact lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Lee, T.D.
1997-09-22
It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.
Advancements in simulations of lattice quantum chromodynamics
International Nuclear Information System (INIS)
Lippert, T.
2008-01-01
An introduction to lattice QCD with emphasis on advanced fermion formulations and their simulation is given. In particular, overlap fermions will be presented, a quite novel fermionic discretization scheme that is able to exactly preserve chiral symmetry on the lattice. I will discuss efficiencies of state-of-the-art algorithms on highly scalable supercomputers and I will show that, due to many algorithmic improvements, overlap simulations will soon become feasible for realistic physical lattice sizes. Finally I am going to sketch the status of some current large scale lattice QCD simulations. (author)
Instantons in the QCD vacuum and in deep inelastic scattering
International Nuclear Information System (INIS)
Ringwald, A.; Schrempp, F.
1999-01-01
We give a brief status report on our on-going investigation of the prospects to discover QCD instantons in deep inelastic scattering (DIS) at HERA. A recent high-quality lattice study of the topological structure of the QCD vacuum is exploited to provide crucial support of our predictions for DIS, based on instanton perturbation theory
Elementary amplitudes from full QCD and the stochastic vacuum model
International Nuclear Information System (INIS)
Martini, A.F.; Menon, M.J.
2002-01-01
In a previous work, making use of the gluon gauge-invariant two-point correlation function determined from lattice QCD in the quenched approximation and the stochastic vacuum model, we determined the elementary (parton-parton) scattering amplitude in the momentum transfer space. In this communication we compute the elementary amplitude from new lattice QCD calculations that include the effects of dynamical fermions (full QCD). The main conclusion is that the inclusion of dynamical fermions leads to a normalized elementary amplitude that decreases more quickly with the momentum transfer than that in the quenched approximation. (author)
Determinations of the QCD strong coupling αsub(s) and the scale Λsub(QCD)
International Nuclear Information System (INIS)
Duke, D.W.; Roberts, R.G.
1984-08-01
The authors review determinations, via experiment of the strong coupling of QCD, αsub(s). In almost every case, the results are used of perturbative QCD to make the necessary extraction from data. These include scaling violations of deep inelastic scattering, e + e - annihilation experiments (including quarkonium decays) and lepton pair production. Finally estimates for Λ from lattice calculations are listed. (author)
QCD thermodynamics from an imaginary μB: Results on the four flavor lattice model
International Nuclear Information System (INIS)
D'Elia, Massimo; Lombardo, Maria-Paola
2004-01-01
We study four flavor QCD at nonzero temperature and density by analytic continuation from an imaginary chemical potential. The explored region is T=0.95T c c , and the baryochemical potentials range from 0 to ≅500 MeV. Observables include the number density, the order parameter for chiral symmetry, and the pressure, which is calculated via an integral method at fixed temperature and quark mass. The simulations are carried out on a 16 3 x4 lattice, and the mass dependence of the results is estimated by exploiting the Maxwell relations. In the hadronic region, we confirm that the results are consistent with a simple resonance hadron gas model, and we estimate the critical density by combining the results for the number density with those for the critical line. In the hot phase, above the end point of the Roberge-Weiss transition T E ≅1.1T c , the results are consistent with a free lattice model with a fixed effective number of flavor slightly different from four. We confirm that confinement and chiral symmetry are coincident by a further analysis of the critical line, and we discuss the interrelation between thermodynamics and critical behavior. We comment on the strength and weakness of the method, and propose further developments
Phase diagram of dense two-color QCD within lattice simulations
Directory of Open Access Journals (Sweden)
Braguta V.V.
2017-01-01
Full Text Available We present the results of a low-temperature scan of the phase diagram of dense two-color QCD with Nf = 2 quarks. The study is conducted using lattice simulation with rooted staggered quarks. At small chemical potential we observe the hadronic phase, where the theory is in a confining state, chiral symmetry is broken, the baryon density is zero and there is no diquark condensate. At the critical point μ = mπ/2 we observe the expected second order transition to Bose-Einstein condensation of scalar diquarks. In this phase the system is still in confinement in conjunction with nonzero baryon density, but the chiral symmetry is restored in the chiral limit. We have also found that in the first two phases the system is well described by chiral perturbation theory. For larger values of the chemical potential the system turns into another phase, where the relevant degrees of freedom are fermions residing inside the Fermi sphere, and the diquark condensation takes place on the Fermi surface. In this phase the system is still in confinement, chiral symmetry is restored and the system is very similar to the quarkyonic state predicted by SU(Nc theory at large Nc.
Measuring infrared contributions to the QCD pressure
Kajantie, Keijo; Rummukainen, K; Schröder, Y
2002-01-01
For the pressure (or free energy) of QCD, four-dimensional (4d) lattice data is available at zero baryon density up to a few times the critical temperature $T_c$. Perturbation theory, on the other hand, has serious convergence problems even at very high temperatures. In a combined analytical and three-dimensional (3d) lattice method, we show that it is possible to compute the QCD pressure from about $2 T_c$ to infinity. The numerical accuracy is good enough to resolve in principle, e.g., logarithmic contributions related to 4-loop perturbation theory.
International Nuclear Information System (INIS)
Hammant, T. C.; Horgan, R. R.; Monahan, C. J.; Hart, A. G.; Hippel, G. M. von
2011-01-01
We present the first application of the background field method to nonrelativistic QCD (NRQCD) on the lattice in order to determine the one-loop radiative corrections to the coefficients of the NRQCD action in a manifestly gauge-covariant manner. The coefficients of the σ·B term in the NRQCD action and the four-fermion spin-spin interaction are computed at the one-loop level; the resulting shift of the hyperfine splitting of bottomonium is found to bring the lattice predictions in line with experiment.
Chiral behavior of K →π l ν decay form factors in lattice QCD with exact chiral symmetry
Aoki, S.; Cossu, G.; Feng, X.; Fukaya, H.; Hashimoto, S.; Kaneko, T.; Noaki, J.; Onogi, T.; Jlqcd Collaboration
2017-08-01
We calculate the form factors of the K →π l ν semileptonic decays in three-flavor lattice QCD and study their chiral behavior as a function of the momentum transfer and the Nambu-Goldstone boson masses. Chiral symmetry is exactly preserved by using the overlap quark action, which enables us to directly compare the lattice data with chiral perturbation theory (ChPT). We generate gauge ensembles at a lattice spacing of 0.11 fm with four pion masses covering 290-540 MeV and a strange quark mass ms close to its physical value. By using the all-to-all quark propagator, we calculate the vector and scalar form factors with high precision. Their dependence on ms and the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields. We compare the results for the semileptonic form factors with ChPT at next-to-next-to-leading order in detail. While many low-energy constants appear at this order, we make use of our data of the light meson electromagnetic form factors in order to control the chiral extrapolation. We determine the normalization of the form factors as f+(0 )=0.9636 (36 )(-35+57) and observe reasonable agreement of their shape with experiment.
Are topological charge fluctuations in QCD instanton dominated?
International Nuclear Information System (INIS)
Edwards, Robert G.; Heller, Urs M.
2002-01-01
We consider a recent proposal by Horvath et al. to address the question of whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings, we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD
Are Topological Charge Fluctuations in QCD Instanton Dominated?
International Nuclear Information System (INIS)
Edwards, Robert G.; Heller, Urs M.
2001-01-01
We consider a recent proposal by Horvath et al. to address the question whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD
The nucleon spin and momentum decomposition using lattice QCD simulations
International Nuclear Information System (INIS)
Alexandrou, C.; Cyprus Univ., Nicosia; Constantinou, M.; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G.; Jansen, K.; Wiese, K.; Vaquero Aviles-Casco, A.
2017-11-01
We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is J u+d+s =0.408(61) stat. (48) syst. and the gluon contribution is J g =0.133(11) stat. (14) syst. giving a total of J N =0.54(6) stat. (5) syst. consistent with the spin sum. For the quark intrinsic spin contribution we obtain (1)/(2)ΔΣ u+d+s =0.201(17) stat. (5) syst. All quantities are given in the MS scheme at 2 GeV. The quark and gluon momentum fractions are also computed and add up to left angle x right angle u+d+s + left angle x right angle g =0.804(121) stat. (95) syst. +0.267(12) stat. (10) syst. =1.07(12) stat. (10) syst. satisfying the momentum sum.
Approach to the thermodynamic limit in lattice QCD at μ≠0
International Nuclear Information System (INIS)
Splittorff, K.; Verbaarschot, J. J. M.
2008-01-01
The expectation value of the complex phase factor of the fermion determinant is computed to leading order in the p expansion of the chiral Lagrangian. The computation is valid for μ π /2 and determines the dependence of the sign problem on the volume and on the geometric shape of the volume. In the thermodynamic limit with L i →∞ at fixed temperature 1/L 0 , the average phase factor vanishes. In the low temperature limit where L i /L 0 is fixed as L i becomes large, the average phase factor approaches 1 for μ π /2. The results for a finite volume compare well with lattice results obtained by Allton et al. After taking appropriate limits, we reproduce previously derived results for the ε regime and for one-dimensional QCD. The distribution of the phase itself is also computed
Energy Technology Data Exchange (ETDEWEB)
Walker-Loud, Andre [College of William and Mary, Williamsburg, VA (United States)
2016-10-14
The research supported by this grant is aimed at probing the limits of the Standard Model through precision low-energy nuclear physics. The work of the PI (AWL) and additional personnel is to provide theory input needed for a number of potentially high-impact experiments, notably, hadronic parity violation, Dark Matter direct detection and searches for permanent electric dipole moments (EDMs) in nucleons and nuclei. In all these examples, a quantitative understanding of low-energy nuclear physics from the fundamental theory of strong interactions, Quantum Chromo-Dynamics (QCD), is necessary to interpret the experimental results. The main theoretical tools used and developed in this work are the numerical solution to QCD known as lattice QCD (LQCD) and Effective Field Theory (EFT). This grant is supporting a new research program for the PI, and as such, needed to be developed from the ground up. Therefore, the first fiscal year of this grant, 08/01/2014-07/31/2015, has been spent predominantly establishing this new research effort. Very good progress has been made, although, at this time, there are not many publications to show for the effort. After one year, the PI accepted a job at Lawrence Berkeley National Laboratory, so this final report covers just a single year of five years of the grant.
Braun-Munzinger, Peter; Redlich, Krzysztof; Stachel, Johanna
2015-01-01
We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge and strangeness from experimental data of the ALICE Collaboration at the CERN LHC. The data were taken in Pb-Pb collisions at $\\sqrt{s_{NN}}$=2.76 TeV. The resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature $T_c\\simeq 155$ MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. The volume of the fireball for one unit of rapidity at $T_c$ is found to exceed 4000 fm$^3$. A detailed discussion on uncertainties in the temperature and volume of the fireball is presented. The results are linked to pion interferometry measurements and predictions from percolation theory.
Effects of QCD equation of state on the stochastic gravitational wave background
Energy Technology Data Exchange (ETDEWEB)
Anand, Sampurn; Mohanty, Subhendra [Physical Research Laboratory, Ahmedabad 380009 (India); Dey, Ujjal Kumar, E-mail: sampurn@prl.res.in, E-mail: ujjal@cts.iitkgp.ernet.in, E-mail: mohanty@prl.res.in [Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721302 (India)
2017-03-01
Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ω{sub gw} of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25% as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.
Computing K and D meson masses with Nf=2+1+1 twisted mass lattice QCD
International Nuclear Information System (INIS)
Baron, Remi; Blossier, Benoit; Boucaud, Philippe
2010-05-01
We discuss the computation of the mass of the K and D mesons within the framework of N f =2+1+1 twisted mass lattice QCD from a technical point of view. These quantities are essential, already at the level of generating gauge configurations, being obvious candidates to tune the strange and charm quark masses to their physical values. In particular, we address the problems related to the twisted mass flavor and parity symmetry breaking, which arise when considering a non-degenerate (c,s) doublet. We propose and verify the consistency of three methods to extract the K and D meson masses in this framework. (orig.)
Lattice study of finite volume effect in HVP for muon g-2
Directory of Open Access Journals (Sweden)
Izubuchi Taku
2018-01-01
Full Text Available We study the finite volume effect of the hadronic vacuum polarization contribution to muon g-2, aμhvp,in lattice QCD by comparison with two different volumes, L4 = (5.44 and (8.14 fm4, at physical pion. We perform the lattice computation of highly precise vector-vector current correlator with optimized AMA technique on Nf = 2 + 1 PACS gauge configurations in Wilson-clover fermion and stout smeared gluon action at one lattice cut-off, a−1 = 2.33 GeV. We compare two integrals of aμhvp, momentum integral and time-slice summation, on the lattice and numerically show that the different size of finite volume effect appears between two methods. We also discuss the effect of backward-state propagation into the result of aμhvp with the different boundary condition. Our model-independent study suggest that the lattice computation at physical pion is important for correct estimate of finite volume and other lattice systematics in aμhvp.
Lattice study of finite volume effect in HVP for muon g-2
Izubuchi, Taku; Kuramashi, Yoshinobu; Lehner, Christoph; Shintani, Eigo
2018-03-01
We study the finite volume effect of the hadronic vacuum polarization contribution to muon g-2, aμhvp, in lattice QCD by comparison with two different volumes, L4 = (5.4)4 and (8.1)4 fm4, at physical pion. We perform the lattice computation of highly precise vector-vector current correlator with optimized AMA technique on Nf = 2 + 1 PACS gauge configurations in Wilson-clover fermion and stout smeared gluon action at one lattice cut-off, a-1 = 2.33 GeV. We compare two integrals of aμhvp, momentum integral and time-slice summation, on the lattice and numerically show that the different size of finite volume effect appears between two methods. We also discuss the effect of backward-state propagation into the result of aμhvp with the different boundary condition. Our model-independent study suggest that the lattice computation at physical pion is important for correct estimate of finite volume and other lattice systematics in aμhvp.
Flavor structure of Λ baryons from lattice QCD: From strange to charm quarks
Gubler, Philipp; Takahashi, Toru T.; Oka, Makoto
2016-12-01
We study Λ baryons of spin-parity 1/2± with either a strange or charm valence quark in full 2 +1 flavor lattice QCD. Multiple S U (3 ) singlet and octet operators are employed to generate the desired single baryon states on the lattice. Via the variational method, the couplings of these states to the different operators provide information about the flavor structure of the Λ baryons. We make use of the gauge configurations of the PACS-CS Collaboration and chirally extrapolate the results for the masses and S U (3 ) flavor components to the physical point. We furthermore gradually change the hopping parameter of the heaviest quark from strange to charm to study how the properties of the Λ baryons evolve as a function of the heavy quark mass. It is found that the baryon energy levels increase almost linearly with the quark mass. Meanwhile, the flavor structure of most of the states remains stable, with the exception of the lowest 1/2- state, which changes from a flavor singlet Λ to a Λc state with singlet and octet components of comparable size. Finally, we discuss whether our findings can be interpreted with the help of a simple quark model and find that the negative-parity Λc states can be naturally explained as diquark excitations of the light u and d quarks. On the other hand, the quark-model picture does not appear to be adequate for the negative-parity Λ states, suggesting the importance of other degrees of freedom to describe them.
Determination of csw in Nf=3+1 lattice QCD with massive Wilson fermions
International Nuclear Information System (INIS)
Stollenwerk, Felix
2017-01-01
In order to obtain sensible results from Lattice QCD that may be compared with experiment, extrapolation to the continuum is crucial. The well-established Symanzik improvement program systematically reduces the order of cutoff effects, allowing for better control of the aforementioned errors, as well as larger and thus more affordable lattice spacings. Applied to the Wilson fermion action, it entails the addition of the Sheikholeslami-Wohlert term with the O(a) improvement coefficient c sw . In this work, a strategy is developed for the non-perturbative determination of c sw in the theory with N f =3+1 massive sea quarks. It is embedded in a general, mass-dependent renormalization and improvement scheme, for which we lay the foundations. The improvement condition, formulated by means of the PCAC relation in the Schroedinger Functional, is imposed along a line of constant physics that is designed to be close to the physical mass of the charm quark. The aim of this rather elaborate approach is to avoid large, mass-dependent O(a 2 ) effects in future large volume simulations with four dynamical quark species. The numerical results are worked out using the tree-level improved Luescher-Weisz gauge action. Since the gradient flow coupling is employed in the definition of the line of constant physics, its interdependence with the topological charge in regard to critical slowing down and topology freezing is investigated in a supplemental study.
Nonperturbative QCD corrections to electroweak observables
Energy Technology Data Exchange (ETDEWEB)
Dru B Renner, Xu Feng, Karl Jansen, Marcus Petschlies
2011-12-01
Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we will examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We will then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we will mention applications to the Adler function, the determination of the strong coupling constant and QCD corrections to muonic-hydrogen.
Form factors for semileptonic Bs→Klν decays in lattice QCD
International Nuclear Information System (INIS)
Bahr, Felix Tobias
2015-01-01
We present an exploratory study of the calculation of the form factor f + (q 2 ) for the semileptonic decay B s →Klν in large-volume lattice QCD simulations with two dynamical sea quark flavours using O(a) improved Wilson fermions. We discuss the computation of relevant two- and three-point functions and consider complementary methods how these can be combined to obtain the form factor. In particular, we put forward the strategy of a combined fit in which data of all correlators enter and which has as fit parameters energies and amplitudes of the correlators and the form factor. The b quark is treated in HQET; our present analysis focuses on the static limit. Meanwhile, we have developed the code and performed the measurements of all needed O(1/m h ) corrections which will be used as soon as their coefficients will have been computed by the ALPHA collaboration. In order to be able to measure the form factor at the same value of the momentum transfer q 2 on all ensembles, we impose twisted boundary conditions on the s and b quarks that allow for a free tuning of the quark momenta and thus of q 2 . We perform measurements on a subset of N f =2 CLS gauge configurations, obtaining the form factor at three different lattice spacings and roughly the same pion mass of about 330 MeV. Using these, we carry out a continuum extrapolation and observe that it is relatively flat in a 2 . A measurement at a different pion mass indicates that quark mass effects are small. We compare our continuum value of the form factor with recently published results of other collaborations and observe a good agreement.
Lattice gauge theory using parallel processors
International Nuclear Information System (INIS)
Lee, T.D.; Chou, K.C.; Zichichi, A.
1987-01-01
The book's contents include: Lattice Gauge Theory Lectures: Introduction and Current Fermion Simulations; Monte Carlo Algorithms for Lattice Gauge Theory; Specialized Computers for Lattice Gauge Theory; Lattice Gauge Theory at Finite Temperature: A Monte Carlo Study; Computational Method - An Elementary Introduction to the Langevin Equation, Present Status of Numerical Quantum Chromodynamics; Random Lattice Field Theory; The GF11 Processor and Compiler; and The APE Computer and First Physics Results; Columbia Supercomputer Project: Parallel Supercomputer for Lattice QCD; Statistical and Systematic Errors in Numerical Simulations; Monte Carlo Simulation for LGT and Programming Techniques on the Columbia Supercomputer; Food for Thought: Five Lectures on Lattice Gauge Theory
Continuum extrapolation of moments of nucleon quark distributions in full QCD
International Nuclear Information System (INIS)
Dreher, P.; Brower, R.; Capitani, S.; Dolgov, D.; Edwards, R.; Eicker, N.; Heller, U.M.; Lippert, Th.; Negele, J.W.; Pochinsky, A.; Renner, D.B.; Schilling, K.
2003-01-01
Moments of light cone quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD at β = 5.5 and β = 5.3 using Wilson fermions on 163 x 32 lattices. These results are combined with earlier calculations at β = 5.6 using SESAM configurations to study the continuum limit
Finite-temperature gluon spectral functions from N{sub f} = 2+1+1 lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, Ernst-Michael; Trunin, Anton [Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); Pawlowski, Jan M. [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung mbH, Darmstadt (Germany); Rothkopf, Alexander [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany)
2018-02-15
We investigate gluon correlation functions and spectral functions at finite temperature in Landau gauge on lattice QCD ensembles with N{sub f} = 2+1+1 dynamical twisted-mass quarks flavors, generated by the tmfT collaboration. They cover a temperature range from 0.8 ≤ T/T{sub C} ≤ 4 using the fixed-scale approach. Our study of spectral properties is based on a novel Bayesian approach for the extraction of non-positive-definite spectral functions. For each binned spatial momentum we take into account the gluon correlation functions at all available discrete imaginary frequencies. Clear indications for the existence of a well defined quasi-particle peak are obtained. Due to a relatively small number of imaginary frequencies available, we focus on the momentum and temperature dependence of the position of this spectral feature. The corresponding dispersion relation reveals different in-medium masses for longitudinal and transversal gluons at high temperatures, qualitatively consistent with weak coupling expectations. (orig.)
Novel fat-link fermion actions for lattice QCD
International Nuclear Information System (INIS)
Zanotti, J.; Bilson-Thompson, S.; Bonnet, F.; Leinweber, D.; Melnitchouk, W.; Williams, A.
2000-01-01
a gauge-invariant manner (APEsmearing). One drawback to this technique is that in smearing the links, one leaves the SU(3) gauge group and one must project back to SU(3), thus losing a rigorous connection to continuum QCD. In addition, one removes the gluon interactions at the scale of the cutoff. While this has some tremendous benefits, one loses short-distance quark interactions. The solution to these problems is to work with two sets of links in the fermion action. In the relevant dimension-four operators, one works with the untouched links generated via Monte Carlo methods. The smeared fat links are introduced only in the higher dimension irrelevant operators. In this way, the continuum limit of the theory is perfectly well defined. Moreover, one can benefit from the favourable aspects of fat links in that the renormalisation of the coefficients of the improvement terms are small and the problems with exceptional configurations are reduced. In this poster we report first results from a novel fat-link fermion action. We evaluate this action through a systematic study of the low-lying hadron mass spectrum and associated dispersion properties
Up, down, strange and charm quark masses with Nf=2+1+1 twisted mass lattice QCD
Directory of Open Access Journals (Sweden)
N. Carrasco
2014-10-01
Full Text Available We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf=2+1+1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their physical values. The simulations are based on a unitary setup for the two light quarks and on a mixed action approach for the strange and charm quarks. The analysis uses data at three values of the lattice spacing and pion masses in the range 210–450 MeV, allowing for accurate continuum limit and controlled chiral extrapolation. The quark mass renormalization is carried out non-perturbatively using the RI′-MOM method. The results for the quark masses converted to the MS¯ scheme are: mud(2 GeV=3.70(17 MeV, ms(2 GeV=99.6(4.3 MeV and mc(mc=1.348(46 GeV. We obtain also the quark mass ratios ms/mud=26.66(32 and mc/ms=11.62(16. By studying the mass splitting between the neutral and charged kaons and using available lattice results for the electromagnetic contributions, we evaluate mu/md=0.470(56, leading to mu=2.36(24 MeV and md=5.03(26 MeV.
Lattice studies of quark spectra and supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Schierenberg, Sebastian
2012-01-01
In the first part of this work, we study quark spectra at either non-zero temperature or chemical potential. In the first case, we find a possible explanation for the Anderson localization that is observed in the spectrum. We introduce a random matrix model that has the same localization and shares other important properties of the QCD Dirac operator, too. In the case of a non-vanishing chemical potential, we show that the eigenvalue spacing distributions of the Dirac operator are described by simple random matrix models. In the second part of this work, we study supersymmetry on the lattice. We summarize our progress with the blocking approach and show possible problems. Furthermore, we construct a lattice action which is improved with respect to supersymmetry and study this action numerically.
Lattice studies of quark spectra and supersymmetric quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Schierenberg, Sebastian
2012-06-24
In the first part of this work, we study quark spectra at either non-zero temperature or chemical potential. In the first case, we find a possible explanation for the Anderson localization that is observed in the spectrum. We introduce a random matrix model that has the same localization and shares other important properties of the QCD Dirac operator, too. In the case of a non-vanishing chemical potential, we show that the eigenvalue spacing distributions of the Dirac operator are described by simple random matrix models. In the second part of this work, we study supersymmetry on the lattice. We summarize our progress with the blocking approach and show possible problems. Furthermore, we construct a lattice action which is improved with respect to supersymmetry and study this action numerically.
Study of shear viscosity of SU(2)-gluodynamics within lattice simulation
Energy Technology Data Exchange (ETDEWEB)
Astrakhantsev, N.Yu. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); Moscow Institute of Physics and Technology,Dolgoprudny, 141700 (Russian Federation); Braguta, V.V. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); Institute for High Energy Physics NRC “Kurchatov Institute”,Protvino, 142281 Russian Federation (Russian Federation); Far Eastern Federal University, School of Biomedicine,Vladivostok, 690950 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),Kashirskoe highway, 31, Moscow, 115409 (Russian Federation); Kotov, A.Yu. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),Kashirskoe highway, 31, Moscow, 115409 (Russian Federation)
2015-09-14
This paper is devoted to the study of two-point correlation function of the energy-momentum tensor 〈T{sub 12}T{sub 12}〉 for SU(2)-gluodynamics within lattice simulation of QCD. Using multilevel algorithm we carried out the measurement of the correlation function at the temperature T/T{sub c}≃1.2. It is shown that lattice data can be described by spectral functions which interpolate between hydrodynamics at low frequencies and asymptotic freedom at high frequencies. The results of the study of spectral functions allowed us to estimate the ratio of shear viscosity to the entropy density η/s=0.134±0.057.
The nucleon spin and momentum decomposition using lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Constantinou, M. [Temple Univ., Philadelphia, PA (United States). Dept. of Physics; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Jansen, K.; Wiese, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Vaquero Aviles-Casco, A. [Utah Univ., Salt Lake City, UT (United States). Dept. of Physics and Astronomy
2017-11-15
We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is J{sub u+d+s}=0.408(61){sub stat.}(48){sub syst.} and the gluon contribution is J{sub g}=0.133(11){sub stat.}(14){sub syst.} giving a total of J{sub N}=0.54(6){sub stat.}(5){sub syst.} consistent with the spin sum. For the quark intrinsic spin contribution we obtain (1)/(2)ΔΣ{sub u+d+s}=0.201(17){sub stat.}(5){sub syst.} All quantities are given in the MS scheme at 2 GeV. The quark and gluon momentum fractions are also computed and add up to left angle x right angle {sub u+d+s}+ left angle x right angle {sub g}=0.804(121){sub stat.}(95){sub syst.}+0.267(12){sub stat.}(10){sub syst.}=1.07(12) {sub stat.}(10){sub syst.} satisfying the momentum sum.
Simulations of dimensionally reduced effective theories of high temperature QCD
Hietanen, Ari
Quantum chromodynamics (QCD) is the theory describing interaction between quarks and gluons. At low temperatures, quarks are confined forming hadrons, e.g. protons and neutrons. However, at extremely high temperatures the hadrons break apart and the matter transforms into plasma of individual quarks and gluons. In this theses the quark gluon plasma (QGP) phase of QCD is studied using lattice techniques in the framework of dimensionally reduced effective theories EQCD and MQCD. Two quantities are in particular interest: the pressure (or grand potential) and the quark number susceptibility. At high temperatures the pressure admits a generalised coupling constant expansion, where some coefficients are non-perturbative. We determine the first such contribution of order g^6 by performing lattice simulations in MQCD. This requires high precision lattice calculations, which we perform with different number of colors N_c to obtain N_c-dependence on the coefficient. The quark number susceptibility is studied by perf...
Hadron-hadron potentials from lattice quantum chromodynamics
International Nuclear Information System (INIS)
Rabitsch, K.
1997-10-01
Problems in nuclear physics generally involve several nucleons due to the composite structure of the atomic nucleus. To study such systems one has to solve the Schroedinger equation and therefore has to know a nucleon-nucleon potential. Experimental data and theoretical considerations indicate that nucleons consist of constituent particles, called quarks. Today, Quantum Chromodynamics (QCD) is believed to be the fundamental theory of strong interactions. Consequently, one should try to understand the nucleon-nucleon interaction from first principles of QCD. At nucleonic distances the strong coupling constant is large. Thus, a perturbative treatment of QCD low energy phenomena is not adequate. However, the formulation of QCD on a four-dimensional Euclidean lattice (lattice QCD) makes it possible to address the nonperturbative aspects of the theory. This approach has already produced valuable results. For example, the confinement of quarks in a nucleon has been demonstrated, and hadron masses have been calculated In this thesis various methods to extract the hadron-hadron interactions from first principles of lattice QCD are presented. One possibility is to consider systems of two static hadrons. A comparison of results in pure gluonic vacuum and with sea quarks is given for both the confinement and the deconfinement phase of QCD. Numerical simulations yield attractive potentials in the overlap region of the hadrons for all considered systems. In the deconfinement phase the resulting potentials are shallower reflecting the dissolution of the hadrons. A big step towards the simulation of realistic two-hadron systems on the lattice is the consideration of mesons consisting of dynamic valence quarks. This is done for the two most important fermionic discretization schemes in the pure gluonic vacuum. A calculation in coordinate space utilizing Kogut-Susskind fermions for the valence quarks yields meson-meson potentials with a long ranged interaction, an intermediate
Quasi-particle model for lattice QCD: quark-gluon plasma in heavy ion collisions
International Nuclear Information System (INIS)
Chandra, Vinod; Ravishankar, V.
2009-01-01
We propose a quasi-particle model to describe the lattice QCD equation of state for pure SU(3) gauge theory in its deconfined state, for T≥1.5T c . The method involves mapping the interaction part of the equation of state to an effective fugacity of otherwise non-interacting quasi-gluons. We find that this mapping is exact. Using the quasi-gluon distribution function, we determine the energy density and the modified dispersion relation for the single particle energy, in which the trace anomaly is manifest. As an application, we first determine the Debye mass, and then the important transport parameters, viz., the shear viscosity, η, and the shear viscosity to entropy density ratio, η/S. We find that both η and η/S are sensitive to the interactions, and that the interactions significantly lower both η and η/S. (orig.)
Exploratory study of the three-gluon vertex on the lattice
Energy Technology Data Exchange (ETDEWEB)
Parrinello, C. (Department of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH93JZ (United Kingdom))
1994-10-01
We define and evaluate on the lattice the amputated three-gluon vertex function in momentum space. We give numerical results for 16[sup 3][times]40 and 24[sup 3][times]40 quenched lattices at [beta]=6.0. A good numerical signal is obtained at the price of enforcing the gauge-fixing condition with high accuracy. By comparing results from two different lattice volumes, we try to investigate the crucial issue of finite volume effects. We also outline a method for the lattice evaluation of the QCD running coupling as defined from the three-gluon vertex, while being aware that a realistic calculation will require larger [beta] values and very high statistics.
Lattice quantum chromodynamics
International Nuclear Information System (INIS)
Hassenfratz, P.
1983-01-01
It is generally accepted that relativistic field theory is relevant in high energy physics. It is also recognized that even in QCD, which is asymptotically free, the scope of perturbation theory is very limited. Despite the tremendous theoretical and experimental effort to study scaling, scaling violations, e + e - , lepton pair creation, jets, etc., the answer to the question whether and to what extent is QCD the theory of strong interactions is vague. At present-day energies it is difficult to disentangle perturbative and non-perturbative effects. The author states that QCD must be understood and that quantitative non-perturbative methods are needed. He states that the lattice formulation of field theories is a promising approach to meeting this need and discusses the formulation in detail in this paper
Neutron Electric Dipole Moment on the Lattice
Yoon, Boram; Bhattacharya, Tanmoy; Gupta, Rajan
2018-03-01
For the neutron to have an electric dipole moment (EDM), the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.
Neutron Electric Dipole Moment on the Lattice
Directory of Open Access Journals (Sweden)
Yoon Boram
2018-01-01
Full Text Available For the neutron to have an electric dipole moment (EDM, the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.
Quark virtuality and QCD vacuum condensates
International Nuclear Information System (INIS)
Zhou Lijuan; Ma Weixing
2004-01-01
Based on the Dyson-Schwinger equations (DSEs) in the 'rainbow' approximation, the authors investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, authors calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ u,d 2 =0.7 GeV 2 for u, d quarks, and λ s 2 =1.6 GeV 2 for s quark. The theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions
Opportunities, Challenges, and Fantasies in Lattice QCD
Wilczek, Frank
2002-01-01
Some important problems in quantitative QCD will certainly yield to hard work and adequate investment of resources, others appear difficult but may be accessible, and still others will require essentially new ideas. Here I identify several examples in each class.
Static QCD potential at rQCD-1: Perturbative expansion and operator-product expansion
International Nuclear Information System (INIS)
Sumino, Y.
2007-01-01
We analyze the static QCD potential V QCD (r) in the distance region 0.1 fm QCD (r) analytically. Higher-order terms are estimated by large-β 0 approximation or by renormalization group, and the renormalization scale is varied around the minimal-sensitivity scale. A 'Coulomb'+linear potential can be identified with the scale-independent and renormalon-free part of the prediction and can be separated from the renormalon-dominating part. (II) In the frame of OPE, we define two types of renormalization schemes for the leading Wilson coefficient. One scheme belongs to the class of conventional factorization schemes. The other scheme belongs to a new class, which is independent of the factorization scale, derived from a generalization of the Coulomb+linear potential of (I). The Wilson coefficient is free from IR renormalons and IR divergences in both schemes. We study properties of the Wilson coefficient and of the corresponding nonperturbative contribution δE US (r) in each scheme. (III) We compare numerically perturbative predictions of the Wilson coefficient and lattice computations of V QCD (r) when n l =0. We confirm either correctness or consistency (within uncertainties) of the theoretical predictions made in (II). Then we perform fits to simultaneously determine δE US (r) and r 0 Λ MS 3-loop (relation between lattice scale and Λ MS ). As for the former quantity, we improve bounds as compared to the previous determination; as for the latter quantity, our analysis provides a new method for its determination. We find that (a) δE US (r)=0 is disfavored, and (b) r 0 Λ MS 3-loop =0.574±0.042. We elucidate the mechanism for the sensitivities and examine sources of errors in detail
Meson Spectroscopy from QCD - Project Results
Energy Technology Data Exchange (ETDEWEB)
Dudek, Jozef [Old Dominion Univ., Norfolk, VA (United States)
2017-04-17
Highlights of the research include: the determination of the form of the lowest energy gluonic excitation within QCD and the spectrum of hybrid hadrons which follows; the first calculation of the spectrum of hybrid baryons within a first-principles approach to QCD; a detailed mapping out of the phase-shift of elastic ππ scattering featuring the ρ resonance at two values of the light quark mass within lattice QCD; the first (and to date, only) determinations of coupled-channel meson-meson scattering within first-principles QCD; the first (and to date, only) determinations of the radiative coupling of a resonant state, the ρ appearing in πγ→ππ; the first (and to date, only) determination of the properties of the broad σ resonance in elastic ππ scattering within QCD without unjustified approximations.
Confinining properties of QCD in strong magnetic backgrounds
Directory of Open Access Journals (Sweden)
Bonati Claudio
2017-01-01
Full Text Available Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.
Nonperturbative QCD corrections to electroweak observables
Energy Technology Data Exchange (ETDEWEB)
Renner, Dru B. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Feng, Xu [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Petschlies, Marcus [The Cyprus Institute, Nicosia (Cyprus)
2012-06-15
Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements, effective field theory techniques and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we mention applications to the Adler function, which can be used to determine the strong coupling constant, and QCD corrections to muonic-hydrogen.
A remark on the large difference between the glueball mass and T sub c in quenched QCD
Ishii, N
2003-01-01
The lattice QCD studies indicate that the critical temperature T sub c approx =260-280 MeV of the deconfinement phase transition in quenched QCD is considerably smaller than the lowest-lying glueball mass m sub G approx =1500-1700 MeV, i.e., T sub c <
Harrison, Judd; Davies, Christine T. H.; Wingate, Matthew; Hpqcd Collaboration
2018-03-01
We present results of a lattice QCD calculation of B →D* and Bs→Ds* axial vector matrix elements with both states at rest. These zero recoil matrix elements provide the normalization necessary to infer a value for the CKM matrix element |Vc b| from experimental measurements of B¯ 0→D*+ℓ-ν ¯ and B¯s0→Ds*+ℓ-ν¯ decay. Results are derived from correlation functions computed with highly improved staggered quarks (HISQ) for light, strange, and charm quark propagators, and nonrelativistic QCD for the bottom quark propagator. The calculation of correlation functions employs MILC Collaboration ensembles over a range of three lattice spacings. These gauge field configurations include sea quark effects of charm, strange, and equal-mass up and down quarks. We use ensembles with physically light up and down quarks, as well as heavier values. Our main results are FB→D *(1 )=0.895 ±0.01 0stat±0.024sys and FBs→Ds*(1 )=0.883 ±0.01 2stat±0.02 8sys . We discuss the consequences for |Vc b| in light of recent investigations into the extrapolation of experimental data to zero recoil.
The exotic atoms of QCD: glueballs, hybrids and baryonia
International Nuclear Information System (INIS)
Barnes, T.
1984-05-01
The theoretical basis underlying the expected ''exotic'' states in QCD, the theory of quarks and gluons, is reviewed in three lectures. The first lecture is an historical introduction to QCD. The second lecture is a critical review of the MIT bag model and QCD on a lattice. The status of three candidate ''exotic'' states seen in psi radiative decays, the i(1440), O(1700) and zeta(2220) are discussed in the third lecture. (author)
Parallel tempering in full QCD with Wilson fermions
International Nuclear Information System (INIS)
Ilgenfritz, E.-M.; Kerler, W.; Mueller-Preussker, M.; Stueben, H.
2002-01-01
We study the performance of QCD simulations with dynamical Wilson fermions by combining the hybrid Monte Carlo algorithm with parallel tempering on 10 4 and 12 4 lattices. In order to compare tempered with standard simulations, covariance matrices between subensembles have to be formulated and evaluated using the general properties of autocorrelations of the parallel tempering algorithm. We find that rendering the hopping parameter κ dynamical does not lead to an essential improvement. We point out possible reasons for this observation and discuss more suitable ways of applying parallel tempering to QCD
Inverse magnetic catalysis from improved holographic QCD in the Veneziano limit
International Nuclear Information System (INIS)
Gürsoy, Umut; Iatrakis, Ioannis; Järvinen, Matti; Nijs, Govert
2017-01-01
We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that B acts constructively on the chiral condensate, a phenomenon called “magnetic catalysis”. In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called “inverse magnetic catalysis”. Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.
Inverse magnetic catalysis from improved holographic QCD in the Veneziano limit
Energy Technology Data Exchange (ETDEWEB)
Gürsoy, Umut; Iatrakis, Ioannis [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena,Utrecht University,Leuvenlaan 4, 3584 CE Utrecht (Netherlands); Järvinen, Matti [Laboratoire de Physique Théorique de l’École Normale Supérieure & Institut de Physique Théorique Philippe Meyer, PSL Research University,CNRS, Sorbonne Universités, UPMC University Paris 06,24 rue Lhomond, 75231 Paris Cedex 05 (France); Nijs, Govert [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena,Utrecht University,Leuvenlaan 4, 3584 CE Utrecht (Netherlands)
2017-03-09
We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that B acts constructively on the chiral condensate, a phenomenon called “magnetic catalysis”. In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called “inverse magnetic catalysis”. Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.
Status and future of lattice gauge theory
International Nuclear Information System (INIS)
Hoek, J.
1989-07-01
The current status of lattice Quantum Chromo Dynamics (QCD) calculations, the computer requirements to obtain physical results and the direction computing is taking are described. First of all, there is a lot of evidence that QCD is the correct theory of strong interactions. Since it is an asymptotically free theory we can use perturbation theory to solve it in the regime of very hard collisions. However even in the case of very hard parton collisions the end-results of the collisions are bound states of quarks and perturbation theory is not sufficient to calculate these final stages. The way to solve the theory in this regime was opened by Wilson. He contemplated replacing the space-time continuum by a discrete lattice, with a lattice spacing a. Continuum physics is then recovered in the limit where the correlation length of the theory, say ξ. is large with respect to the lattice spacing. This will be true if the lattice spacing becomes very small, which for asymptotically free theories also implies that the coupling g becomes small. The lattice approach to QCD is in many respects analogous to the use of finite element methods to solve classical field theories. These finite element methods are easy to apply in 2-dimensional simulations but are computationally demanding in the 3-dimensional case. Therefore it is not unexpected that the 4-dimensional simulations needed for lattice gauge theories have led to an explosion in demand for computing power by theorists. (author)
The Operator Product Expansion Beyond Perturbation Theory in QCD
International Nuclear Information System (INIS)
Dominguez, C. A.
2011-01-01
The Operator Product Expansion (OPE) of current correlators at short distances beyond perturbation theory in QCD, together with Cauchy's theorem in the complex energy plane, are the pillars of the method of QCD sum rules. This technique provides an analytic tool to relate QCD with hadronic physics at low and intermediate energies. It has been in use for over thirty years to determine hadronic parameters, form factors, and QCD parameters such as the quark masses, and the running strong coupling at the scale of the τ-lepton. QCD sum rules provide a powerful complement to numerical simulations of QCD on the lattice. In this talk a short review of the method is presented for non experts, followed by three examples of recent applications.
Controlling quark mass determinations non-perturbatively in three-flavour QCD
Campos, Isabel
2017-01-01
The determination of quark masses from lattice QCD simulations requires a non-perturbative renormalization procedure and subsequent scale evolution to high energies, where a conversion to the commonly used MS-bar scheme can be safely established. We present our results for the non-perturbative running of renormalized quark masses in Nf=3 QCD between the electroweak and a hadronic energy scale, where lattice simulations are at our disposal. Recent theoretical advances in combination with well-established techniques allows to follow the scale evolution to very high statistical accuracy, and full control of systematic effects.
QCD-instantons and conformal space-time inversion symmetry
International Nuclear Information System (INIS)
Klammer, D.
2008-04-01
In this paper, we explore the appealing possibility that the strong suppression of large-size QCD instantons - as evident from lattice data - is due to a surviving conformal space-time inversion symmetry. This symmetry is both suggested from the striking invariance of highquality lattice data for the instanton size distribution under inversion of the instanton size ρ→(left angle ρ right angle 2 )/(ρ) and from the known validity of space-time inversion symmetry in the classical instanton sector. We project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via conformal stereographic mapping, before investigating conformal inversion. This projection to a compact, curved geometry is both to avoid the occurence of divergences and to introduce the average instanton size left angle ρ right angle from the lattice data as a new length scale. The average instanton size is identified with the radius b of this 5d-sphere and acts as the conformal inversion radius. For b= left angle ρ right angle, our corresponding results are almost perfectly symmetric under space-time inversion and in good qualitative agreement with the lattice data. For (ρ)/(b)→0 we recover the familiar results of instanton perturbation theory in flat 4d-space. Moreover, we illustrate that a (weakly broken) conformal inversion symmetry would have significant consequences for QCD beyond instantons. As a further successful test for inversion symmetry, we present striking implications for another instanton dominated lattice observable, the chirality-flip ratio in the QCD vacuum. (orig.)
Up and Down Quark Masses and Corrections to Dashen's Theorem from Lattice QCD and Quenched QED.
Fodor, Z; Hoelbling, C; Krieg, S; Lellouch, L; Lippert, Th; Portelli, A; Sastre, A; Szabo, K K; Varnhorst, L
2016-08-19
In a previous Letter [Borsanyi et al., Phys. Rev. Lett. 111, 252001 (2013)] we determined the isospin mass splittings of the baryon octet from a lattice calculation based on N_{f}=2+1 QCD simulations to which QED effects have been added in a partially quenched setup. Using the same data we determine here the corrections to Dashen's theorem and the individual up and down quark masses. Our ensembles include 5 lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and average up-down quark masses all the way down to their physical value. For the parameter which quantifies violations to Dashen's theorem, we obtain ϵ=0.73(2)(5)(17), where the first error is statistical, the second is systematic, and the third is an estimate of the QED quenching error. For the light quark masses we obtain, m_{u}=2.27(6)(5)(4) and m_{d}=4.67(6)(5)(4) MeV in the modified minimal subtraction scheme at 2 GeV and the isospin breaking ratios m_{u}/m_{d}=0.485(11)(8)(14), R=38.2(1.1)(0.8)(1.4), and Q=23.4(0.4)(0.3)(0.4). Our results exclude the m_{u}=0 solution to the strong CP problem by more than 24 standard deviations.
Hadron scattering, resonances, and QCD
Briceño, R. A.
2016-11-01
The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.
Computing K and D meson masses with N{sub f}=2+1+1 twisted mass lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Baron, Remi [CEA, Centre de Saclay, 91 - Gif-sur-Yvette (France). IRFU/Service de Physique Nucleaire; Blossier, Benoit; Boucaud, Philippe [Paris XI Univ., 91 - Orsay (FR). Lab. de Physique Theorique] (and others)
2010-05-15
We discuss the computation of the mass of the K and D mesons within the framework of N{sub f}=2+1+1 twisted mass lattice QCD from a technical point of view. These quantities are essential, already at the level of generating gauge configurations, being obvious candidates to tune the strange and charm quark masses to their physical values. In particular, we address the problems related to the twisted mass flavor and parity symmetry breaking, which arise when considering a non-degenerate (c,s) doublet. We propose and verify the consistency of three methods to extract the K and D meson masses in this framework. (orig.)
Properties of pseudoscalar flavor singlet mesons from lattice QCD
International Nuclear Information System (INIS)
Ottnad, Konstantin
2014-01-01
The central topic of this work are masses and mixing parameters of the η-η' system, which are investigated within the framework of Wilson twisted mass lattice QCD, using gauge configurations provided by the European Twisted Mass Collaboration. We present the first calculation with N f =2+1+1 dynamical quark flavors performed at three different values of the lattice spacing and multiple values of the light quark mass, corresponding to charged pion masses ranging from ∝230 MeV to ∝500 MeV. Moreover, we use selected ensembles which differ only by the value of the strange quark mass while all other parameters are kept fixed in order to obtain information on the strange quark mass dependence of our observables. This allows us to carry out chiral and continuum extrapolations with well-controlled systematics for the mass of the η meson. Using the standard method, the statistical error for the η' turns out significantly larger due to the large contributions of quark disconnected diagrams and autocorrelation effects. However, employing an improved analysis method based on an excited state subtraction in the connected pieces of the correlation function matrix, it becomes feasible to obtain a result for the η' mass with controlled systematics as well. The values for both masses M η =551(8) stat (6) sys MeV and M η' =1006(54) stat (38) sys (+64) ex MeV turn out to be in excellent agreement with experiment. Considering matrix elements in the quark-flavor basis, one expects the mixing in the η-η' system to be described reasonably well by a single mixing angle φ and two decay constants f l , f s . The required accuracy of the matrix elements is again guaranteed by the aforementioned, improved analysis method, yielding a value of φ=46.0(0.9) stat (2.7) sys circle for the mixing angle extrapolated to the physical point. In addition we obtain results for the ratios f l /f PS =0.859(07) stat (64) sys and f s /f K =1.166(11) stat (31) sys . We find that our data is
Lattice theory for nonspecialists
International Nuclear Information System (INIS)
Hari Dass, N.D.
1984-01-01
These lectures were delivered as part of the academic training programme at the NIKHEF-H. These lectures were intended primarily for experimentalists, and theorists not specializing in lattice methods. The goal was to present the essential spirit behind the lattice approach and consequently the author has concentrated mostly on issues of principle rather than on presenting a large amount of detail. In particular, the author emphasizes the deep theoretical infra-structure that has made lattice studies meaningful. At the same time, he has avoided the use of heavy formalisms as they tend to obscure the basic issues for people trying to approach this subject for the first time. The essential ideas are illustrated with elementary soluble examples not involving complicated mathematics. The following subjects are discussed: three ways of solving the harmonic oscillator problem; latticization; gauge fields on a lattice; QCD observables; how to solve lattice theories. (Auth.)
The world according to lattice QCD
International Nuclear Information System (INIS)
Sharpe, S.R.
1988-12-01
A non-technical introduction to lattice calculations is given. The successes and problems of current calculations are emphasized. A summary of lattice results on non-exotic meson and baryon masses indicates that while calculations in the quenched approximation are becoming reliable, the results differ in systematic ways from the physical values. Results for exotic mesons (glueballs and hybrids) are then presented. The future prospects are discussed. 23 refs., 4 figs
The hadronic vacuum polarization contribution to the muon g - 2 from lattice QCD
Morte, M. Della; Francis, A.; Gülpers, V.; Herdoíza, G.; von Hippel, G.; Horch, H.; Jäger, B.; Meyer, H. B.; Nyffeler, A.; Wittig, H.
2017-10-01
We present a calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, a μ hvp , in lattice QCD employing dynamical up and down quarks. We focus on controlling the infrared regime of the vacuum polarization function. To this end we employ several complementary approaches, including Padé fits, time moments and the time-momentum representation. We correct our results for finite-volume effects by combining the Gounaris-Sakurai parameterization of the timelike pion form factor with the Lüscher formalism. On a subset of our ensembles we have derived an upper bound on the magnitude of quark-disconnected diagrams and found that they decrease the estimate for a μ hvp by at most 2%. Our final result is {a}_{μ}^{hvp} = (654 ± {32}{^{-23}}^{+21}) ·10-10, where the first error is statistical, and the second denotes the combined systematic uncertainty. Based on our findings we discuss the prospects for determining a μ hvp with sub-percent precision.
Axion phenomenology and θ-dependence from N{sub f}=2+1 lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Bonati, Claudio; D’Elia, Massimo; Mariti, Marco [Dipartimento di Fisica dell’Università di Pisa, Largo Pontecorvo 3, I-56127 Pisa (Italy); INFN sezione di Pisa,Largo Pontecorvo 3, I-56127 Pisa (Italy); Martinelli, Guido [Dipartimento di Fisica dell’Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma (Italy); INFN Sezione di Roma La Sapienza,Piazzale Aldo Moro 5, I-00185 Roma (Italy); Mesiti, Michele [Dipartimento di Fisica dell’Università di Pisa, Largo Pontecorvo 3, I-56127 Pisa (Italy); INFN sezione di Pisa,Largo Pontecorvo 3, I-56127 Pisa (Italy); Negro, Francesco [INFN sezione di Pisa,Largo Pontecorvo 3, I-56127 Pisa (Italy); Sanfilippo, Francesco [School of Physics and Astronomy, University of Southampton,SO17 1BJ Southampton (United Kingdom); Villadoro, Giovanni [Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34151, Trieste (Italy)
2016-03-22
We investigate the topological properties of N{sub f}=2+1 QCD with physical quark masses, both at zero and finite temperature. We adopt stout improved staggered fermions and explore a range of lattice spacings a∼0.05−0.12 fm. At zero temperature we estimate both finite size and finite cut-off effects, comparing our continuum extrapolated results for the topological susceptibility χ with predictions from chiral perturbation theory. At finite temperature, we explore a region going from T{sub c} up to around 4 T{sub c}, where we provide continuum extrapolated results for the topological susceptibility and for the fourth moment of the topological charge distribution. While the latter converges to the dilute instanton gas prediction the former differs strongly both in the size and in the temperature dependence. This results in a shift of the axion dark matter window of almost one order of magnitude with respect to the instanton computation.
Light hadron spectrum in 2+1 flavor full QCD by CP-PACS and JLQCD Collaborations
International Nuclear Information System (INIS)
Ishikawa, T.; Aoki, S.; Fukugita, M.; Hashimoto, S.; Ishikawa, K-I.; Ishizuka, N.; Iwasaki, Y.; Kanaya, K.; Kaneko, T.; Kuramashi, Y.; Okawa, M.; Onogi, T.; Taniguchi, N.; Tsutsui, N.; Ukawa, A.; Yoshie, T.
2005-01-01
CP-PACS and JLQCD Collaborations are carrying out a joint project of the 2+1 flavor full QCD with the RG-improved gauge action and the non-perturbatively O(a)-improved Wilson quark action. This simulation removes quenching effects of all three light quarks, which is the last major uncertainty in lattice QCD. In this report we present our results for the light meson spectrum and quark masses on a 20 3 x40 lattice at the lattice spacing a∼0.10 fm
Energy Technology Data Exchange (ETDEWEB)
Dru Renner, Xu Feng, Karl Jansen, Marcus Petschlies
2011-08-01
We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, infinite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modification to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513 (43) 10^-12, 5.72 (16) 10^-8 and 2.650 (54) 10^-6 for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%.
Hadronic vacuum polarization contribution to {a}_{\mu} from full lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, Bipasha; Davies, C. T. H.; de Oliveira, P. G.; Koponen, J.; Lepage, G. P.; Van de Water, R. S.
2017-08-01
We determine the contribution to the anomalous magnetic moment of the muon from the $\\alpha^2_{\\mathrm{QED}}$ hadronic vacuum polarization diagram using full lattice QCD and including $u/d$ quarks with physical masses for the first time. We use gluon field configurations that include $u$, $d$, $s$ and $c$ quarks in the sea at multiple values of the lattice spacing, multiple $u/d$ masses and multiple volumes that allow us to include an analysis of finite-volume effects. We obtain a result for $a_{\\mu}^{\\mathrm{HVP,LO}}$ of $667(6)(12)$, where the first error is from the lattice calculation and the second includes systematic errors from missing QED and isospin-breaking effects and from quark-line disconnected diagrams. Our result implies a discrepancy between the experimental determination of $a_{\\mu}$ and the Standard Model of 3$\\sigma$.
Using a commercial symmetric multiprocessor for lattice QCD
International Nuclear Information System (INIS)
Brower, R.C.; Chen, D.; Negele, J.W.
1998-01-01
In its evolution, the computer industry has reached the point when considerable computing power can be packaged on a single microprocessor chip. At the same time, costs of designing a computer system around such a CPU are growing. For these reasons we decided to explore a possibility of using commercially available symmetric multiprocessors (SMP) as building blocks for the LQCD computer. Careful analysis of the architecture allowed us to build a QCD primitive library running close to the peak performance on the UltraSPARC processor. As a result, multithreaded QCD code (both the heatbath and the Wilson fermion inverter) runs at about 50% efficiency on a single SMP. The communication between different CPUs is handled by a coherent memory system. Currently we are planning to connect several SMPs with a high bandwidth network into a single system. (orig.)
Lattice NRQCD study on in-medium bottomonium spectra using a novel Bayesian reconstruction approach
Kim, Seyong; Petreczky, Peter; Rothkopf, Alexander
2016-01-01
We present recent results on the in-medium modification of S- and P-wave bottomonium states around the deconfinement transition. Our study uses lattice QCD with Nf = 2 + 1 light quark flavors to describe the non-perturbative thermal QCD medium between 140MeV Bayesian prescription, which provides higher accuracy than the Maximum Entropy Method. Based on a systematic comparison of interacting and free spectral functions we conclude that the ground states of both the S-wave (ϒ) and P-wave (χb1) channel survive up to T = 249MeV. Stringent upper limits on the size of the in-medium modification of bottomonium masses and widths are provided.
Fermion frontiers in vector lattice gauge theories: Proceedings. Volume 8
International Nuclear Information System (INIS)
1998-01-01
The inclusion of fermions into simulations of lattice gauge theories is very difficult both theoretically and numerically. With the presence of Teraflops-scale computers for lattice gauge theory, the authors wanted a forum to discuss new approaches to lattice fermions. The workshop concentrated on approaches which are ripe for study on such large machines. Although lattice chiral fermions are vitally important to understand, there is not technique at hand which is viable on these Teraflops-scale machines for real-world problems. The discussion was therefore focused on recent developments and future prospects for QCD-like theories. For the well-known fermion formulations, the Aoki phase in Wilson fermions, novelties of U A (1) symmetry and the η' for staggered fermions and new approaches for simulating the determinant for Wilson fermions were discussed. The newer domain-wall fermion formulation was reviewed, with numerical results given by many speakers. The fermion proposal of Friedberg, Lee and Pang was introduced. They also were able to compare and contrast the dependence of QCD and QCD-like SUSY theories on the number of quark flavors. These proceedings consist of several transparencies and a summary page from each speaker. This should serve to outline the major points made in each talk
Energy Technology Data Exchange (ETDEWEB)
Brambilla, M.; Di Renzo, F. [Universita di Parma (Italy); INFN, Gruppo Collegato di Parma, Dipartimento di Fisica e Scienze della Terra, Parma (Italy); Hasegawa, M. [Universita di Parma (Italy); Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); INFN, Gruppo Collegato di Parma, Dipartimento di Fisica e Scienze della Terra, Parma (Italy)
2014-07-15
This is the third of a series of papers on three-loop computation of renormalization constants for Lattice QCD. Our main points of interest are results for the regularization defined by the Iwasaki gauge action and n{sub f} Wilson fermions. Our results for quark bilinears renormalized according to the RI'-MOM scheme can be compared to non-perturbative results. The latter are available for twisted mass QCD: being defined in the chiral limit, the renormalization constants must be the same. We also address more general problems. In particular, we discuss a few methodological issues connected to summing the perturbative series such as the effectiveness of boosted perturbation theory and the disentanglement of irrelevant and finite-volume contributions. Discussing these issues we consider not only the new results of this paper, but also those for the regularization defined by the tree-level Symanzik improved gauge action and n{sub f} Wilson fermions, which we presented in a recent paper of ours. We finally comment on the extent to which the techniques we put at work in the NSPT context can provide a fresher look into the lattice version of the RI'-MOM scheme. (orig.)
A BHLS model based moment analysis of muon g-2, and its use for lattice QCD evaluations of ahadμ
International Nuclear Information System (INIS)
Benayoun, M.; DelBuono, L.
2016-05-01
We present an up-to-date analysis of muon g-2 evaluations in terms of Mellin-Barnes moments as they might be useful for lattice QCD calculations of a μ . The moments up to 4th order are evaluated directly in terms of e + e - -annihilation data and improved within the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking mechanisms. The model provides a reliable Effective Lagrangian (BHLS) estimate of the two-body channels plus the πππ channel up to 1.05 GeV, just including the φ resonance. The HLS piece accounts for 80% of the contribution to a μ . The missing pieces are evaluated in the standard way directly in terms of the data. We find that the moment expansion converges well in terms of a few moments. The two types of moments which show up in the Mellin-Barnes representation are calculated in terms of hadronic cross-section data in the timelike region and in terms of the hadronic vacuum polarization (HVP) function in the spacelike region which is accessible to lattice QCD (LQCD). In the Euclidean the first type of moments are the usual Taylor coefficients of the HVP and we show that the second type of moments may be obtained as integrals over the appropriately Taylor truncated HVP function. Specific results for the isovector part of a had μ are determined by means of HLS model predictions in close relation to τ-decay spectra.
The renormalization group and lattice QCD
International Nuclear Information System (INIS)
Gupta, R.
1989-01-01
This report discusses the following topics: scaling of thermodynamic quantities and critical exponents; scaling relations; block spin idea of Kadanoff; exact RG solution of the 1-d Ising model; Wilson's formulation of the renormalization group; linearized transformation matrix and classification of exponents; derivation of exponents from the eigenvalues of Τ αβ ; simple field theory: the gaussian model; linear renormalization group transformations; numerical methods: MCRG; block transformations for 4-d SU(N) LGT; asymptotic freedom makes QCD simple; non-perturbative β-function and scaling; and the holy grail: the renormalized trajectory
Sea quark matrix elements and flavor singlet spectroscopy on the lattice
International Nuclear Information System (INIS)
Lagae, J.F.
1996-01-01
I summarize the results of three recent lattice studies which use stochastic estimator techniques in order to investigate the flavor singlet dynamics in QCD. These include a measurement of the pion-nucleon σ-term, the computation of the flavor singlet axial coupling constant of the nucleon and a determination of flavor singlet meson screening lengths in finite temperature QCD
Gluon structure function of a color dipole in the light-cone limit of lattice QCD
International Nuclear Information System (INIS)
Gruenewald, D.; Ilgenfritz, E.-M.; Pirner, H. J.
2009-01-01
We calculate the gluon structure function of a color dipole in near-light-cone SU(2) lattice QCD as a function of x B . The quark and antiquark are external nondynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. We compute the color dipole matrix element of transversal chromo-electric and chromo-magnetic field operators separated along a direction close to the light cone, the Fourier transform of which is the gluon structure function. As vacuum state in the pure glue sector, we use a variational ground state of the near-light-cone Hamiltonian. We derive a recursion relation for the gluon structure function on the lattice similar to the perturbative Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. It depends on the number of transversal links assembling the Schwinger string of the dipole. Fixing the mean momentum fraction of the gluons to the 'experimental value' in a proton, we compare our gluon structure function for a dipole state with four links with the next-to-leading-order MRST 2002 and the CTEQ AB-0 parametrizations at Q 2 =1.5 GeV 2 . Within the systematic uncertainty we find rather good agreement. We also discuss the low x B behavior of the gluon structure function in our model calculation.
The lowest Landau level in QCD
Directory of Open Access Journals (Sweden)
Bruckmann Falk
2017-01-01
Full Text Available The thermodynamics of Quantum Chromodynamics (QCD in external (electro-magnetic fields shows some unexpected features like inverse magnetic catalysis, which have been revealed mainly through lattice studies. Many effective descriptions, on the other hand, use Landau levels or approximate the system by just the lowest Landau level (LLL. Analyzing lattice configurations we ask whether such a picture is justified. We find the LLL to be separated from the rest by a spectral gap in the two-dimensional Dirac operator and analyze the corresponding LLL signature in four dimensions. We determine to what extent the quark condensate is LLL dominated at strong magnetic fields.
National Computational Infrastructure for Lattice Gauge Theory: Final report
International Nuclear Information System (INIS)
Reed, Daniel A.
2008-01-01
In this document we describe work done under the SciDAC-1 Project National Computerational Infrastructure for Lattice Gauge Theory. The objective of this project was to construct the computational infrastructure needed to study quantum chromodynamics (QCD). Nearly all high energy and nuclear physicists in the United States working on the numerical study of QCD are involved in the project, as are Brookhaven National Laboratory (BNL), Fermi National Accelerator Laboratory (FNAL), and Thomas Jefferson National Accelerator Facility (JLab). A list of the senior participants is given in Appendix A.2. The project includes the development of community software for the effective use of the terascale computers, and the research and development of commodity clusters optimized for the study of QCD. The software developed as part of this effort is publicly available, and is being widely used by physicists in the United States and abroad. The prototype clusters built with SciDAC-1 fund have been used to test the software, and are available to lattice gauge theorists in the United States on a peer reviewed basis
Simulating QCD at finite density
de Forcrand, Philippe
2009-01-01
In this review, I recall the nature and the inevitability of the "sign problem" which plagues attempts to simulate lattice QCD at finite baryon density. I present the main approaches used to circumvent the sign problem at small chemical potential. I sketch how one can predict analytically the severity of the sign problem, as well as the numerically accessible range of baryon densities. I review progress towards the determination of the pseudo-critical temperature T_c(mu), and towards the identification of a possible QCD critical point. Some promising advances with non-standard approaches are reviewed.
Searching for new physics at the frontiers with lattice quantum chromodynamics.
Van de Water, Ruth S
2012-07-01
Numerical lattice-quantum chromodynamics (QCD) simulations, when combined with experimental measurements, allow the determination of fundamental parameters of the particle-physics Standard Model and enable searches for physics beyond-the-Standard Model. We present the current status of lattice-QCD weak matrix element calculations needed to obtain the elements and phase of the Cabibbo-Kobayashi-Maskawa (CKM) matrix and to test the Standard Model in the quark-flavor sector. We then discuss evidence that may hint at the presence of new physics beyond the Standard Model CKM framework. Finally, we discuss two opportunities where we expect lattice QCD to play a pivotal role in searching for, and possibly discovery of, new physics at upcoming high-intensity experiments: rare decays and the muon anomalous magnetic moment. The next several years may witness the discovery of new elementary particles at the Large Hadron Collider (LHC). The interplay between lattice QCD, high-energy experiments at the LHC, and high-intensity experiments will be needed to determine the underlying structure of whatever physics beyond-the-Standard Model is realized in nature. © 2012 New York Academy of Sciences.
High temperature QCD with three flavors of improved staggered quarks
International Nuclear Information System (INIS)
Bernard, C.; Burch, T.; Tar, C.E. de; Gottlieb, Steven; Gregory, Eric; Heller, U.M.; Osborn, J.; Sugar, R.L.; Toussaint, D.
2003-01-01
We present an update of our study of high temperature QCD with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad staggered quark action. Simulations are being carried out on lattices with N t = 4, 6 and 8 for the case of three degenerate quarks with masses less than or equal to the strange quark mass, m s and on lattices with N t = 6 and 8 for degenerate up and down quarks with masses in the range 0.2m s ≤ m u,d ≤ 0.6m s and the strange quark fixed near its physical value. We also report on first computations of quark number susceptibilities with the Asqtad action. These susceptibilities are of interest because they can be related to event-by-event fluctuations in heavy ion collision experiments. Use of the improved quark action leads to a substantial reduction in lattice artifacts. This can be seen already for free fermions and carries over into our results for QCD
Constraints on СS and Їј ¯ from lattice quantum chromo- dynamics
Indian Academy of Sciences (India)
Relevance of these results to estimates of б. ' /б is discussed. Keywords. Lattice QCD ... Their values depend on the QCD renormalization scale, and three quantitative approaches have been used to .... Numerical results show that, for a fixed value of the lattice scale, increasing N increases the coupling g¾ through vacuum ...
Energy Technology Data Exchange (ETDEWEB)
Feng, Xu [DESY, Zeuthen (Germany). NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Jansen, Karl; Renner, Dru B. [DESY, Zeuthen (Germany). NIC; Petschlies, Marcus [Humboldt Univ. Berlin (Germany). Inst. fuer Physik
2011-03-15
We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, in nite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modi cation to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513(43).10{sup -12}, 5.72(16).10{sup -8} and 2.650(54).10{sup -6} for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%. (orig.)
Deflation for inversion with multiple right-hand sides in QCD
International Nuclear Information System (INIS)
Stathopoulos, A; Abdel-Rehim, A M; Orginos, K
2009-01-01
Most calculations in lattice Quantum Chromodynamics (QCD) involve the solution of a series of linear systems of equations with exceedingly large matrices and a large number of right hand sides. Iterative methods for these problems can be sped up significantly if we deflate approximations of appropriate invariant spaces from the initial guesses. Recently we have developed eigCG, a modification of the Conjugate Gradient (CG) method, which while solving a linear system can reuse a window of the CG vectors to compute eigenvectors almost as accurately as the Lanczos method. The number of approximate eigenvectors can increase as more systems are solved. In this paper we review some of the characteristics of eigCG and show how it helps remove the critical slowdown in QCD calculations. Moreover, we study scaling with lattice volume and an extension of the technique to nonsymmetric problems.
Nonperturbative determination of the QCD potential at O(1/m)
International Nuclear Information System (INIS)
Koma, Y.; Koma, M.; Wittig, H.
2006-07-01
The relativistic correction to the QCD static inter-quark potential at O(1/m) is investigated nonperturbatively for the first time by using lattice Monte Carlo QCD simulations. The correction is found to be comparable with the Coulombic term of the static potential when applied to charmonium, and amounts to 26% of the Coulombic term for bottomonium. (Orig.)
New perspectives for heavy flavour physics from the lattice
Energy Technology Data Exchange (ETDEWEB)
Sommer, R. [John von Neumann-Institut fuer Computing NIC/DESY, Zeuthen (Germany)
2009-06-15
Heavy flavours represent a challenge for lattice QCD. We discuss it in very general terms. We give an idea of the significant recent progress which opens up good perspectives for high precision first principles QCD computations for flavour physics. (orig.)
New perspectives for heavy flavour physics from the lattice
International Nuclear Information System (INIS)
Sommer, R.
2009-06-01
Heavy flavours represent a challenge for lattice QCD. We discuss it in very general terms. We give an idea of the significant recent progress which opens up good perspectives for high precision first principles QCD computations for flavour physics. (orig.)
Quark–hadron phase structure, thermodynamics, and magnetization of QCD matter
Nasser Tawfik, Abdel; Magied Diab, Abdel; Hussein, M. T.
2018-05-01
The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.
Search for the QCD critical point at SPS energies
Anticic, T.; Barna, D.; Bartke, J.; Betev, L.; Bialkowska, H.; Blume, C.; Boimska, B.; Botje, M.; Bracinik, J.; Buncic, P.; Cerny, V.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Csato, P.; Dinkelaker, P.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gal, J.; Gazdzicki, M.; Genchev, V.; Gladysz, E.; Grebieszkow, K.; Hegyi, S.; Hohne, C.; Kadija, K.; Karev, A.; Kikola, D.; Kolesnikov, V.I.; Kornas, E.; Korus, R.; Kowalski, M.; Kreps, M.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Levai, P.; Litov, L.; Lungwitz, B.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mischke, A.; Mitrovski, M.; Mrowczynski, St.; Palla, G.; Panagiotou, A.D.; Petridis, A.; Peryt, W.; Pikna, M.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Sitar, B.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strabel, C.; Strobele, H.; Susa, T.; Szentpetery, I.; Sziklai, J.; Szuba, M.; Szymanski, P.; Trubnikov, V.; Utvic, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Wojtaszek-Szwarc, A.; Yoo, I.K.; Abgrall, N.; Aduszkiewicz, A.; Andrieu, B.; Anticic, T.; Antoniou, N.; Argyriades, J.; Asryan, A.G.; Blondel, A.; Blumer, J.; Boldizsar, L.; Bravar, A.; Brzychczyk, J.; Bubak, A.; Bunyatov, S.A.; Choi, K.-U.; Chung, P.; Cleymans, J.; Derkach, D.A.; Diakonos, F.; Dominik, W.; Dumarchez, J.; Engel, R.; Ereditato, A.; Feofilov, G.A.; Ferrero, A.; Gazdzicki, M.; Golubeva, M.; Grzeszczuk, A.; Guber, F.; Hasegawa, T.; Haungs, A.; Igolkin, S.; Ivanov, A.S.; Ivashkin, A.; Katrynska, N.; Kielczewska, D.; Kisiel, J.; Kobayashi, T.; Kolev, D.; Kolevatov, R.S.; Kondratiev, V.P.; Kowalski, S.; Kurepin, A.; Lacey, R.; Lyubushkin, V.V.; Majka, Z.; Marchionni, A.; Marcinek, A.; Maris, I.; Matveev, V.; Meregaglia, A.; Messina, M.; Mijakowski, P.; Montaruli, T.; Murphy, S.; Nakadaira, T.; Naumenko, P.A.; Nikolic, V.; Nishikawa, K.; Palczewski, T.; Planeta, R.; Popov, B.A.; Posiadala, M.; Przewlocki, P.; Rauch, W.; Ravonel, M.; Rohrich, D.; Rondio, E.; Rossi, B.; Roth, M.; Rubbia, A.; Sadovsky, A.; Sakashita, K.; Sekiguchi, T.; Seyboth, P.; Shibata, M.; Sissakian, A.N.; Sorin, A.S.; Staszel, P.; Stepaniak, J.; Strabel, C.; Stroebele, H.; Tada, M.; Taranenko, A.; Tsenov, R.; Ulrich, R.; Unger, M.; Vechernin, V.V.; Zipper, W.
2009-01-01
Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.
The running QCD coupling in the pre-asymptotic region
Energy Technology Data Exchange (ETDEWEB)
Burgio, G.; Di Renzo, F.; Parrinello, C.; Pittori, C
1999-03-01
We study deviations from the perturbative asymptotic behaviour in the running QCD coupling by analysing non-perturbative measurements of {alpha}{sub s}(p) at low momenta (p {approx} 2 GeV) as obtained from the lattice three-gluon vertex. Our exploratory study provides some evidence for power corrections to the perturbative running proportional to 1/p{sup 2}.
Exploring the nucleon structure from first principles of QCD
Energy Technology Data Exchange (ETDEWEB)
Bietenholz, W. [Universidad Nacional Autonoma de Mexico (Mexico). Inst. de Ciencias Nucleares; Cundy, N.; Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)
2010-04-15
Quantum Chromodynamics (QCD) is generally assumed to be the fundamental theory underlying nuclear physics. In recent years there is progress towards investigating the nucleon structure from first principles of QCD. Although this structure is best revealed in Deep Inelastic Scattering, a consistent analysis has to be performed in a fully non-perturbative scheme. The only known method for this purpose are lattice simulations. We first sketch the ideas of Monte Carlo simulations in lattice gauge theory. Then we comment in particular on the issues of chiral symmetry and operator mixing. Finally we present our results for the Bjorken variable of a single quark, and for the second Nachtmann moment of the nucleon structure functions. (orig.)
Exploring the nucleon structure from first principles of QCD
International Nuclear Information System (INIS)
Bietenholz, W.; Cundy, N.; Goeckeler, M.
2010-04-01
Quantum Chromodynamics (QCD) is generally assumed to be the fundamental theory underlying nuclear physics. In recent years there is progress towards investigating the nucleon structure from first principles of QCD. Although this structure is best revealed in Deep Inelastic Scattering, a consistent analysis has to be performed in a fully non-perturbative scheme. The only known method for this purpose are lattice simulations. We first sketch the ideas of Monte Carlo simulations in lattice gauge theory. Then we comment in particular on the issues of chiral symmetry and operator mixing. Finally we present our results for the Bjorken variable of a single quark, and for the second Nachtmann moment of the nucleon structure functions. (orig.)
Towards 4-loop NSPT result for a 3-dimensional condensate-contribution to hot QCD pressure
Torrero, C.; Schroder, Y.; Di Renzo, F.; Miccio, V.
2007-01-01
Thanks to dimensional reduction, the contributions to the hot QCD pressure coming from so-called soft modes can be studied via an effective three-dimensional theory named Electrostatic QCD (spatial Yang-Mills fields plus an adjoint Higgs scalar). The poor convergence of the perturbative series within EQCD suggests to perform lattice measurements of some of the associated gluon condensates. These turn out, however, to be plagued by large discretization artifacts. We discuss how Numerical Stochastic Perturbation Theory can be exploited to determine the full lattice spacing dependence of one of these condensates up to 4-loop order, and sharpen our tools on a concrete 2-loop example.
Strong evidence for spontaneous chiral symmetry breaking in (quenched) QCD
International Nuclear Information System (INIS)
Barbour, I.M.; Gibbs, P.; Schierholz, G.; Teper, M.; Gilchrist, J.P.; Schneider, H.
1983-09-01
We calculate the chiral condensate for all quark masses using Kogut-Susskind fermions in lattice-regularized quenched QCD. The large volume behaviour of at small quark masses demonstrates that the explicit U(1) chiral symmetry is spontaneously broken. We perform the calculation for β = 5.1 to 5.9 and find very good continuum renormalization group behaviour. We infer that the spontaneous breaking we observe belongs to continuum QCD. This constitutes the first unambiguous demonstration of spontaneous chiral symmetry breaking in continuum quenched QCD. (orig.)
Gauge field theories on a || lattice
International Nuclear Information System (INIS)
Burkardt, Matthias
1999-01-01
In these notes, the transverse || lattice approach is presented as a means to control the k + →0 divergences in light-front QCD. Technical difficulties of both the canonical compact formulation as well as the non-compact formulation of the || lattice motivate the color-dielectric formulation, where the link fields are linearized
On the absence of pentaquark states from dynamics in strongly coupled lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Anjos, Petrus Henrique Ribeiro dos [Universidade Federal de Goias (UFG), Goiania, GO (Brazil); Veiga, Paulo Afonso Faria da; O' Carroll, Michael [Universidade de Sao Paulo (USP), SP (Brazil); Francisco Neto, Antonio [Universidade Federal de Ouro Preto (UFOP), MG (Brazil)
2011-07-01
Full text: We consider an imaginary time functional integral formulation of a two-flavor, 3 + 1 lattice QCD model with Wilson's action and in the strong coupling regime (with a small hopping parameter, {kappa}0, and a much smaller plaquette coupling, {beta} = 1/g{sub 0}{sup 2}, so that the quarks and glueballs are heavy). The model has local SU(3){sub c} gauge and global SU(2){sub f} flavor symmetries, and incorporates the corresponding part of the eightfold way particles: baryons (mesons) of asymptotic mass -3ln{kappa}(-2 ln {kappa}). We search for pentaquark states as meson-baryon bound states in the energy-momentum spectrum of the model, using a lattice Bethe-Salpeter equation. This equation is solved within a ladder approximation, given by the lowest nonvanishing order in {kappa} and {beta} of the Bethe-Salpeter kernel. It includes order 2 contributions with a q-barq exchange potential together with a contribution that is a local-in-space, energy-dependent potential. The attractive or repulsive nature of the exchange interaction depends on the spin of the meson-baryon states. The Bethe-Salpeter equation presents integrable singularities, forcing the couplings to be above a threshold value for the meson and the baryon to bind in a pentaquark. We analyzed all the total isospin sectors, I = 1/2/3/2/ 5/2, for the system. For all I, the net attraction resulting from the two sources of interaction is not strong enough for the meson and the baryon to bind. Thus, within our approximation, these pentaquark states are not present up to near the free meson-baryon energy threshold of - 5 ln{kappa}. This result is to be contrasted with the spinless case for which our method detects meson-baryon bound states, as well as for Yukawa effective baryon and meson field models. A physical interpretation of our results emerges from an approximate correspondence between meson-baryon bound states and negative energy states of a one-particle lattice Schroedinger Hamiltonian
International Nuclear Information System (INIS)
Faria da Veiga, Paulo A.; O'Carroll, Michael
2006-01-01
We determine baryon-baryon bound states in (3+1)-dimensional SU(3) lattice QCD with two flavors, 4x4 spin matrices, and in an imaginary time formulation. For small hopping parameter κ>0 and large glueball mass (strong coupling), we show the existence of three-quark isospin 1/2 particles (proton and neutron) and isospin 3/2 baryons (delta particles), with asymptotic masses -3lnκ and isolated dispersion curves. Baryon-baryon bound states of isospin zero are found with binding energy of order κ 2 , using a ladder approximation to a lattice Bethe-Salpeter equation. The dominant baryon-baryon interaction is an energy-independent spatial range-one attractive potential with an O(κ 2 ) strength. There is also attraction arising from gauge field correlations associated with six overlapping bonds, but it is counterbalanced by Pauli repulsion to give a vanishing zero-range potential. The overall range-one potential results from a quark, antiquark exchange with no meson exchange interpretation; the repulsive or attractive nature of the interaction depends on the isospin and spin of the two-baryon state
Spectroscopy of hadron resonances on the lattice
Energy Technology Data Exchange (ETDEWEB)
Bali, Gunnar; Burch, Tommy; Ehmann, Christian; Goeckeler, Meinulf; Hagen, Christian; Schaefer, Andreas [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Gattringer, Christof; Lang, Christian; Limmer, Markus; Mohler, Daniel [Institut fuer Physik, FB Theoretische Physik, Universitaet Graz, A-8010 Graz (Austria)
2009-07-01
The reproduction of the hadron mass spectrum from first principles is an important task for lattice QCD. While ground state spectroscopy, especially in the quenched approximation, is by now well understood, a clean extraction of excited hadron masses from a lattice QCD simulation still is a serious challenge. We discuss the relevant techniques for spectroscopy calculations on the lattice, in particular the variational technique which is needed for separating the different excited states from the ground state. Using this method we study three different sectors of the hadron spectrum. In the light quark sector we present hadron masses obtained from simulations with dynamical approximately chiral fermions, so-called Chirally Improved Fermions. For charmonium, we are able to extract masses for a number of excited states including ones with higher spin and exotic quantum numbers. The heavy-light hadron sector is investigated in the static-light approximation, i.e., the heavy quark is treated as infinitely heavy. Also here we are able to determine a large number of excitations.
Generalized parton distributions and transversity from full lattice QCD
Göckeler, M.; Hägler, Ph.; Horsley, R.; Pleiter, D.; Rakow, P. E. L.; Schäfer, A.; Schierholz, G.; Zanotti, J. M.; Qcdsf Collaboration
2005-06-01
We present here the latest results from the QCDSF collaboration for moments of gener- alized parton distributions and transversity in two-flavour QCD, including a preliminary analysis of the pion mass dependence.
Double-beta decay processes from lattice quantum chromodynamics
Davoudi, Zohreh; Tiburzi, Brian; Wagman, Michael; Winter, Frank; Chang, Emmanuel; Detmold, William; Orginos, Kostas; Savage, Martin; Shanahan, Phiala; Nplqcd Collaboration
2017-09-01
While an observation of neutrinoless double-beta decay in upcoming experiments will establish that the neutrinos are Majorana particles, the underlying new physics responsible for this decay can only be constrained if the theoretical predictions of the rate are substantially refined. This talk demonstrates the roadmap in connecting the underlying high-scale theory to the corresponding nuclear matrix elements, focusing mainly on the nucleonic matrix elements in the simplest extension of Standard Model in which a light Majorana neutrino is mediating the process. The role of lattice QCD and effective field theory in this program, in particular, the prospect of a direct matching of the nn to pp amplitude to lattice QCD will be discussed. As a first step towards this goal, the results of the first lattice QCD calculation of the relevant matrix element for neutrinofull double-beta decay will be presented, albeit with unphysical quark masses, along with important lessons that could impact the calculations of nuclear matrix elements involved in double-beta decays of realistic nuclei.
Non-perturbative Debye mass in finite-T QCD
Kajantie, Keijo; Peisa, J; Rajantie, A; Rummukainen, K; Shaposhnikov, Mikhail E
1997-01-01
Employing a non-perturbative gauge invariant definition of the Debye screening mass m_D in the effective field theory approach to finite T QCD, we use 3d lattice simulations to determine the leading O(g^2) and to estimate the next-to-leading O(g^3) corrections to m_D in the high temperature region. The O(g^2) correction is large and modifies qualitatively the standard power-counting hierarchy picture of correlation lengths in high temperature QCD.