WorldWideScience

Sample records for anisotropic lattice qcd

  1. Spectral functions from anisotropic lattice QCD

    Science.gov (United States)

    Aarts, G.; Allton, C.; Amato, A.; Evans, W.; Giudice, P.; Harris, T.; Kelly, A.; Kim, S. Y.; Lombardo, M. P.; Praki, K.; Ryan, S. M.; Skullerud, J.-I.

    2016-12-01

    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.

  2. 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.

  3. Penta-quark baryon in anisotropic lattice QCD

    CERN Document Server

    Ishii, N; Iida, H; Oka, M; Okiharu, F; Suganuma, H

    2005-01-01

    The penta-quark(5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized anisotropy a_s/a_t=4 for a high-precision mass measurement. The standard Wilson action at beta=5.75 and the O(a) improved Wilson quark action with kappa=0.1210(0.0010)0.1240 are employed on a 12^3 \\times 96 lattice. Contribution of excited states is suppressed by using a smeared source. We investigate both the positive- and negative-parity 5Q baryons with I=0 and spin J=1/2 using a non-NK-type interpolating field. After chiral extrapolation, the lowest positive-parity state is found to have a mass, m_{Theta}=2.25 GeV, which is much heavier than the experimentally observed Theta^+(1540). The lowest negative-parity 5Q appears at m_{Theta}=1.75 GeV, which is near the s-wave NK threshold. To distinguish spatially-localized 5Q resonances from NK scattering states, we propose a new general method imposing a ``Hybrid Boundary Condition (HBC)'', where the NK threshold is artificially raised without affecting compact five-quark...

  4. Hybrid Charmonium from Lattice QCD

    CERN Document Server

    Luo, X Q

    2006-01-01

    We review our recent results on the JPC = 0¡¡ exotic hybrid charmonium mass and JPC = 0¡+, 1¡¡ and 1++ nonexotic hybrid charmonium spectrum from anisotropic improved lattice QCD and discuss the relevance to the recent discovery of the Y(4260) state and future experimental search for other states.

  5. Phenomenology from lattice QCD

    CERN Document Server

    Lellouch, L P

    2003-01-01

    After a short presentation of lattice QCD and some of its current practical limitations, I review recent progress in applications to phenomenology. Emphasis is placed on heavy-quark masses and on hadronic weak matrix elements relevant for constraining the CKM unitarity triangle. The main numerical results are highlighted in boxes.

  6. QCD thermodynamics on a lattice

    Science.gov (United States)

    Levkova, Ludmila A.

    Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with two flavors of dynamical staggered fermions, where all bare parameters and the renormalized anisotropy are kept constant and the temperature is changed in small steps by varying only the number of time slices. Including results from zero-temperature scale setting simulations, which determine the Karsch coefficients, allows for the calculation of the Equation of State at finite temperatures. We also report on studies of the chiral properties of dynamical domain-wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations at stronger couplings.

  7. Introduction to lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, R.

    1998-12-31

    The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.

  8. Lattice QCD on fine lattices

    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.

  9. Kenneth Wilson and lattice QCD

    CERN Document Server

    Ukawa, Akira

    2015-01-01

    We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward b...

  10. Nuclear Reactions from Lattice QCD

    CERN Document Server

    Briceño, Raúl A; Luu, Thomas C

    2014-01-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path ...

  11. Berry phase in lattice QCD

    CERN Document Server

    Yamamoto, Arata

    2016-01-01

    We propose the lattice QCD calculation of the Berry phase which is defined by the ground state of a single fermion. We perform the ground-state projection of a single-fermion propagator, construct the Berry link variable on a momentum-space lattice, and calculate the Berry phase. As the first application, the first Chern number of the (2+1)-dimensional Wilson fermion is calculated by the Monte Carlo simulation.

  12. Lattice gauge theory for QCD

    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.

  13. Lattice QCD: A Brief Introduction

    Science.gov (United States)

    Meyer, H. B.

    A general introduction to lattice QCD is given. The reader is assumed to have some basic familiarity with the path integral representation of quantum field theory. Emphasis is placed on showing that the lattice regularization provides a robust conceptual and computational framework within quantum field theory. The goal is to provide a useful overview, with many references pointing to the following chapters and to freely available lecture series for more in-depth treatments of specifics topics.

  14. Extracting Electric Polarizabilities from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Will Detmold, William Detmold, Brian Tiburzi, Andre Walker-Loud

    2009-05-01

    Charged and neutral, pion and kaon electric polarizabilities are extracted from lattice QCD using an ensemble of anisotropic gauge configurations with dynamical clover fermions. We utilize classical background fields to access the polarizabilities from two-point correlation functions. Uniform background fields are achieved by quantizing the electric field strength with the proper treatment of boundary flux. These external fields, however, are implemented only in the valence quark sector. A novel method to extract charge particle polarizabilities is successfully demonstrated for the first time.

  15. Nucleon structure using lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.

    2013-03-15

    A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.

  16. 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.

  17. 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.

  18. Lattice QCD simulations beyond the quenched approximation

    Energy Technology Data Exchange (ETDEWEB)

    Ukawa, A. (European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.)

    1989-07-01

    Present status of lattice QCD simulations incorporating the effects of dynamical quarks is presented. After a brief review of the formalism of lattice QCD, the dynamical fermion algorithms in use today are described. Recent attempts at the hadron mass calculation are discussed in relation to the quenched results, and current understanding on the finite temperature behavior of QCD is summarized. (orig.).

  19. Topics in lattice QCD and effective field theory

    Science.gov (United States)

    Buchoff, Michael I.

    Quantum Chromodynamics (QCD) is the fundamental theory that governs hadronic physics. However, due to its non-perturbative nature at low-energy/long distances, QCD calculations are difficult. The only method for performing these calculations is through lattice QCD. These computationally intensive calculations approximate continuum physics with a discretized lattice in order to extract hadronic phenomena from first principles. However, as in any approximation, there are multiple systematic errors between lattice QCD calculation and actual hardronic phenomena. Developing analytic formulae describing the systematic errors due to the discrete lattice spacings is the main focus of this work. To account for these systematic effects in terms of hadronic interactions, effective field theory proves to be useful. Effective field theory (EFT) provides a formalism for categorizing low-energy effects of a high-energy fundamental theory as long as there is a significant separation in scales. An example of this is in chiral perturbation theory (chiPT), where the low-energy effects of QCD are contained in a mesonic theory whose applicability is a result of a pion mass smaller than the chiral breaking scale. In a similar way, lattice chiPT accounts for the low-energy effects of lattice QCD, where a small lattice spacing acts the same way as the quark mass. In this work, the basics of this process are outlined, and multiple original calculations are presented: effective field theory for anisotropic lattices, I=2 pipi scattering for isotropic, anisotropic, and twisted mass lattices. Additionally, a combination of effective field theory and an isospin chemical potential on the lattice is proposed to extract several computationally difficult scattering parameters. Lastly, recently proposed local, chiral lattice actions are analyzed in the framework of effective field theory, which illuminates various challenges in simulating such actions.

  20. Innovations in Lattice QCD Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Konstantinos Orginos

    2006-06-25

    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.

  1. Scale setting in lattice QCD

    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.

  2. Hadron Physics from Lattice QCD

    OpenAIRE

    2016-01-01

    We sketch the basic ideas of the lattice regularization in Quantum Field Theory, the corresponding Monte Carlo simulations, and applications to Quantum Chromodynamics (QCD). This approach enables the numerical measurement of observables at the non-perturbative level. We comment on selected results, with a focus on hadron masses and the link to Chiral Perturbation Theory. At last we address two outstanding issues: topological freezing and the sign problem.

  3. 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.

  4. Lattice QCD for nuclear physics

    CERN Document Server

    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...

  5. Flavor Physics and Lattice QCD

    CERN Document Server

    Bouchard, C M

    2013-01-01

    Our ability to resolve new physics effects is, largely, limited by the precision with which we calculate. The calculation of observables in the Standard (or a new physics) Model requires knowledge of associated hadronic contributions. The precision of such calculations, and therefore our ability to leverage experiment, is typically limited by hadronic uncertainties. The only first-principles method for calculating the nonperturbative, hadronic contributions is lattice QCD. Modern lattice calculations have controlled errors, are systematically improvable, and in some cases, are pushing the sub-percent level of precision. I outline the role played by, highlight state of the art efforts in, and discuss possible future directions of lattice calculations in flavor physics.

  6. Hadron structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Green, Jeremy [Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz (Germany)

    2016-01-22

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  7. Hadron Structure from Lattice QCD

    CERN Document Server

    Green, Jeremy

    2014-01-01

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  8. LATTICE QCD THERMODYNAMICS WITH WILSON QUARKS.

    Energy Technology Data Exchange (ETDEWEB)

    EJIRI,S.

    2007-11-20

    We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.

  9. Shear Viscosity from Lattice QCD

    CERN Document Server

    Mages, Simon W; Fodor, Zoltán; Schäfer, Andreas; Szabó, Kálmán

    2015-01-01

    Understanding of the transport properties of the the quark-gluon plasma is becoming increasingly important to describe current measurements at heavy ion collisions. This work reports on recent efforts to determine the shear viscosity h in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. It is carried out at finite Wilson flow time, which eliminates the dependence on the lattice spacing. Eventually, a new continuum limit has to be carried out which sends the new regulator introduced by finite flow time to zero. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed. At the end some quenched results for temperatures up to 4 : 5 T c are presented

  10. Aspects of baryon structure in lattice QCD

    Science.gov (United States)

    Babich, Ronald

    Despite the long success of Quantum Chromodynamics (QCD) as the theory of the strong interactions, there remains much to be understood about the structure of hadrons and the consequences of QCD in the nonperturbative regime. Lattice gauge theory, a framework nearly as old as QCD itself, makes calculations in this regime possible, starting from first principles. With advances in theoretical understanding, methods, and computer technology, the lattice has found application to an ever-widening range of problems. In this dissertation, I consider two such problems having to do with the structure of baryons. The first concerns the contribution of sea quarks, and the strange quark in particular, to form factors of the nucleon. This has been a long-standing challenge for the lattice, because such contributions involve the insertion of a current on a quark loop, demanding the full inversion of the discretized Dirac operator, conceptually a large sparse matrix. I discuss methods for addressing this challenge and present a calculation of the strange scalar form factor and the related parameter fTs. The latter is of great theoretical interest, since it enters into the cross section for the scattering of dark matter off nuclei in supersymmetric extensions of the standard model. As such, it represents a major uncertainty in the interpretation of direct detection experiments. I also present results for the strange quark contribution to the nucleon's axial and electromagnetic form factors, which are themselves the subject of active experimental programs. These calculations were performed using the Wilson fermion formulation on a 243 x 64 anisotropic lattice. In the second part of the dissertation, I turn to the valence sector and address the role of diquark correlations in the observed spectrum of hadrons and their properties. A diquark is a correlated pair of quarks, thought to play an important role in certain phenomenological models of hadrons. I present results for baryon wave

  11. Effective Field Theories and Lattice QCD

    CERN Document Server

    Bernard, C

    2015-01-01

    I describe some of the many connections between lattice QCD and effective field theories, focusing in particular on chiral effective theory, and, to a lesser extent, Symanzik effective theory. I first discuss the ways in which effective theories have enabled and supported lattice QCD calculations. Particular attention is paid to the inclusion of discretization errors, for a variety of lattice QCD actions, into chiral effective theory. Several other examples of the usefulness of chiral perturbation theory, including the encoding of partial quenching and of twisted boundary conditions, are also described. In the second part of the talk, I turn to results from lattice QCD for the low energy constants of the two- and three-flavor chiral theories. I concentrate here on mesonic quantities, but the dependence of the nucleon mass on the pion mass is also discussed. Finally I describe some recent preliminary lattice QCD calculations by the MILC Collaboration relating to the three-flavor chiral limit.

  12. 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

  13. CL2QCD - Lattice QCD based on OpenCL

    CERN Document Server

    Philipsen, Owe; Sciarra, Alessandro; Bach, Matthias

    2014-01-01

    We present the Lattice QCD application CL2QCD, which is based on OpenCL and can be utilized to run on Graphic Processing Units as well as on common CPUs. We focus on implementation details as well as performance results of selected features. CL2QCD has been successfully applied in LQCD studies at finite temperature and density and is available at http://code.compeng.uni-frankfurt.de/projects/clhmc.

  14. 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.

  15. Landau Levels in Lattice QCD

    CERN Document Server

    Bruckmann, Falk; Giordano, Matteo; Katz, Sandor D; Kovacs, Tamas G; Pittler, Ferenc; Wellnhofer, Jacob

    2016-01-01

    The spectrum of the two-dimensional continuum Dirac operator in the presence of a uniform background magnetic field consists of Landau levels, which are degenerate and separated by gaps. On the lattice the Landau levels are spread out by discretization artefacts, but a remnant of their structure is clearly visible (Hofstadter butterfly). If one switches on a non-Abelian interaction, the butterfly structure will be smeared out, but the lowest Landau level (LLL) will still be separated by a gap from the rest of the spectrum. In this talk we discuss how one can define the LLL in QCD and check how well certain physical quantities are approximated by taking into account only the LLL.

  16. Gluonic Transversity from Lattice QCD

    CERN Document Server

    Detmold, W

    2016-01-01

    We present an exploratory study of the gluonic structure of the $\\phi$ meson using lattice QCD (LQCD). This includes the first investigation of gluonic transversity via the leading moment of the twist-two double-helicity-flip gluonic structure function $\\Delta(x,Q^2)$. This structure function only exists for targets of spin $J\\ge1$ and does not mix with quark distributions at leading twist, thereby providing a particularly clean probe of gluonic degrees of freedom. We also explore the gluonic analogue of the Soffer bound which relates the helicity flip and non-flip gluonic distributions, finding it to be saturated at the level of 80%. This work sets the stage for more complex LQCD studies of gluonic structure in the nucleon and in light nuclei where $\\Delta(x,Q^2)$ is an 'exotic glue' observable probing gluons in a nucleus not associated with individual nucleons.

  17. 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.

  18. QCD Factorization and PDFs from Lattice QCD Calculation

    CERN Document Server

    Ma, Yan-Qing

    2014-01-01

    In this talk, we review a QCD factorization based approach to extract parton distribution and correlation functions from lattice QCD calculation of single hadron matrix elements of quark-gluon operators. We argue that although the lattice QCD calculations are done in the Euclidean space, the nonperturbative collinear behavior of the matrix elements are the same as that in the Minkowski space, and could be systematically factorized into parton distribution functions with infrared safe matching coefficients. The matching coefficients can be calculated perturbatively by applying the factorization formalism on to asymptotic partonic states.

  19. Lattice QCD and the CKM matrix

    CERN Document Server

    De Grand, T

    2001-01-01

    These lectures (given at TASI 2000) provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1 (Ch. 2) is a very vanilla introduction to lattice QCD. Lecture 2 (Ch. 3) describes examples of recent lattice calculations relevant to fixing the parameters of the CKM matrix.

  20. LatticeQCD using OpenCL

    CERN Document Server

    Bach, Matthias; Pinke, Christopher; Schäfer, Christian; Zeidlewicz, Lars

    2011-01-01

    We report on our implementation of LatticeQCD applications using OpenCL. We focus on the general concept and on distributing different parts on hybrid systems, consisting of both CPUs (Central Processing Units) and GPUs (Graphic Processing Units).

  1. New Noise Subtraction Methods in Lattice QCD

    CERN Document Server

    Baral, Suman; Morgan, Ronald B

    2016-01-01

    Noise subtraction techniques can help reduce the statistical uncertainty in the extraction of hard to detect signals. We describe new noise subtraction methods in Lattice QCD which apply to disconnected diagram evaluations. Some of the noise suppression techniques include polynomial quark matrix methods, eigenspectrum deflation methods, and combination methods. Our most promising technique combines polynomial and Hermitian deflation subtraction methods. The overall goal is to improve the efficiency of Lattice QCD noise method algorithms.

  2. Lattice QCD and the Jefferson Laboratory Program

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek, Robert Edwards, David Richards, Konstantinos Orginos

    2011-06-01

    Lattice gauge theory provides our only means of performing \\textit{ab initio} calculations in the non-perturbative regime. It has thus become an increasing important component of the Jefferson Laboratory physics program. In this paper, we describe the contributions of lattice QCD to our understanding of hadronic and nuclear physics, focusing on the structure of hadrons, the calculation of the spectrum and properties of resonances, and finally on deriving an understanding of the QCD origin of nuclear forces.

  3. Nuclear reactions from lattice QCD

    Science.gov (United States)

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-02-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, quantum chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three-nucleon (and higher) interactions in a consistent manner. Currently, lattice quantum chromodynamics (LQCD) provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between LQCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from LQCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  4. 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.)

  5. Resummation of Cactus Diagrams in Lattice QCD

    CERN Document Server

    Panagopoulos, H

    1998-01-01

    We show how to perform a resummation, to all orders in perturbation theory, of a certain class of gauge invariant diagrams in Lattice QCD. These diagrams are often largely responsible for lattice artifacts. Our resummation leads to an improved perturbative expansion. Applied to a number of cases of interest, this expansion yields results remarkably close to corresponding nonperturbative estimates.

  6. Exploring Hyperons and Hypernuclei with Lattice QCD

    CERN Document Server

    Beane, S R; Parreño, A; Savage, M J

    2003-01-01

    In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Lambda's, and Sigma's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P-wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Luscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for Lambda-N scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone,...

  7. Strangeness at finite temperature from Lattice QCD

    CERN Document Server

    Noronha-Hostler, Jacquelyn; Gunther, Jana; Parotto, Paolo; Pasztor, Attila; Vazquez, Israel Portillo; Ratti, Claudia

    2016-01-01

    The precision reached by recent lattice QCD results allows for the first time to investigate whether the measured hadronic spectrum is missing some additional strange states, which are predicted by the Quark Model but have not yet been detected. This can be done by comparing some sensitive thermodynamic observables from lattice QCD to the predictions of the Hadron Resonance Gas model (with the inclusion of decays [3]). We propose a set of specific observables, defined as linear combinations of conserved charge fluctuations, which allow to investigate this issue for baryons containing one or more strange quarks separately. Applications of these observables to isolate the multiplicity fluctuations of kaons from lattice QCD, and their comparison with the experimental results, are also discussed.

  8. Exploring hyperons and hypernuclei with lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S.R.; Bedaque, P.F.; Parreno, A.; Savage, M.J.

    2003-01-01

    In this work we outline a program for lattice QCD that wouldprovide a first step toward understanding the strong and weakinteractions of strange baryons. The study of hypernuclear physics hasprovided a significant amount of information regarding the structure andweak decays of light nuclei containing one or two Lambda's, and Sigma's.From a theoretical standpoint, little is known about the hyperon-nucleoninteraction, which is required input for systematic calculations ofhypernuclear structure. Furthermore, the long-standing discrepancies inthe P-wave amplitudes for nonleptonic hyperon decays remain to beunderstood, and their resolution is central to a better understanding ofthe weak decays of hypernuclei. We present a framework that utilizesLuscher's finite-volume techniques in lattice QCD to extract thescattering length and effective range for Lambda-N scattering in both QCDand partially-quenched QCD. The effective theory describing thenonleptonic decays of hyperons using isospin symmetry alone, appropriatefor lattice calculations, is constructed.

  9. String Breaking in Four Dimensional Lattice QCD

    CERN Document Server

    Duncan, A; Thacker, H

    2001-01-01

    Virtual quark pair screening leads to breaking of the string between fundamental representation quarks in QCD. For unquenched four dimensional lattice QCD, this (so far elusive) phenomenon is studied using the recently developed truncated determinant algorithm (TDA). The dynamical configurations were generated on an Athlon 650 MHz PC. Quark eigenmodes up to 420 MeV are included exactly in these TDA studies performed at low quark mass on large coarse (but O($a^2$) improved) lattices. A study of Wilson line correlators in Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical configurations reveals evidence for flattening of the string tension at distances R $\\geq$ approximately 1 fm.

  10. Landau gauge gluon vertices from Lattice QCD

    CERN Document Server

    Duarte, Anthony G; Silva, Paulo J

    2016-01-01

    In lattice QCD the computation of one-particle irreducible (1PI) Green's functions with a large number (> 2) of legs is a challenging task. Besides tuning the lattice spacing and volume to reduce finite size effects, the problems associated with the estimation of higher order moments via Monte Carlo methods and the extraction of 1PI from complete Green's functions are limitations of the method. Herein, we address these problems revisiting the calculation of the three gluon 1PI Green's function.

  11. Meson Resonances from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-06-01

    There has been recent, significant, advances in the determination of the meson spectrum of QCD. Current efforts have focused on the development and application of finite-volume formalisms that allow for the determination of scattering amplitudes as well as resonance behavior in coupled channel systems. I will review some of these recent developments, and demonstrate the viability of the method in meson systems.

  12. Equation of State from Lattice QCD Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Rajan [Los Alamos National Laboratory

    2011-01-01

    We provide a status report on the calculation of the Equation of State (EoS) of QCD at finite temperature using lattice QCD. Most of the discussion will focus on comparison of recent results obtained by the HotQCD and Wuppertal-Budapest collaborations. We will show that very significant progress has been made towards obtaining high precision results over the temperature range of T = 150-700 MeV. The various sources of systematic uncertainties will be discussed and the differences between the two calculations highlighted. Our final conclusion is that these lattice results of EoS are precise enough to be used in the phenomenological analysis of heavy ion experiments at RHIC and LHC.

  13. Kaon-Nucleon potential from lattice QCD

    Directory of Open Access Journals (Sweden)

    Nemura H.

    2010-04-01

    Full Text Available We study the K N interactions in the I(Jπ = 0(1/2− and 1(1/2− channels and associated exotic state Θ+ from 2+1 flavor full lattice QCD simulation for relatively heavy quark mass corresponding to mπ = 871 MeV. The s-wave K N potentials are obtained from the Bethe-Salpeter wave function by using the method recently developed by HAL QCD (Hadrons to Atomic nuclei from Lattice QCD Collaboration. Potentials in both channels reveal short range repulsions: Strength of the repulsion is stronger in the I = 1 potential, which is consistent with the prediction of the Tomozawa-Weinberg term. The I = 0 potential is found to have attractive well at mid range. From these potentials, the K N scattering phase shifts are calculated and compared with the experimental data.

  14. Visualization Tools for Lattice QCD - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Massimo Di Pierro

    2012-03-15

    Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.

  15. Lattice QCD simulation of the Berry curvature

    CERN Document Server

    Yamamoto, Arata

    2016-01-01

    The Berry curvature is a fundamental concept describing topological order of quantum systems. While it can be analytically tractable in non-interacting systems, numerical simulations are necessary in interacting systems. We present a formulation to calculate the Berry curvature in lattice QCD.

  16. Lattice QCD and the Balkan physicists contribution

    CERN Document Server

    Borici, Artan

    2015-01-01

    This is a paper based on the invited talk the author gave at the 9th Balkan Physical Union conference. It contains some of the main achievements of lattice QCD simulations followed by a list of Balkan physicists who have contributed to the project.

  17. Lattice QCD on a Beowulf Cluster

    OpenAIRE

    Kim, Seyong

    1999-01-01

    Using commodity component personal computers based on Alpha processor and commodity network devices and a switch, we built an 8-node parallel computer. GNU/Linux is chosen as an operating system and message passing libraries such as PVM, LAM, and MPICH have been tested as a parallel programming environment. We discuss our lattice QCD project for a heavy quark system on this computer.

  18. Lattice QCD on a Beowulf Cluster

    CERN Document Server

    Kim, S

    2000-01-01

    Using commodity component personal computers based on Alpha processor and commodity network devices and a switch, we built an 8-node parallel computer. GNU/Linux is chosen as an operating system and message passing libraries such as PVM, LAM, and MPICH have been tested as a parallel programming environment. We discuss our lattice QCD project for a heavy quark system on this computer.

  19. Composite operators in lattice QCD nonperturbative renormalization

    CERN Document Server

    Göckeler, M; Oelrich, H; Perlt, H; Petters, D; Rakow, P; Schäfer, A; Schierholz, G; Schiller, A

    1999-01-01

    We investigate the nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields. These include operators which are relevant to the calculation of moments of hadronic structure functions. The computations are based on Monte Carlo simulations using quenched Wilson fermions.

  20. Marking up lattice QCD configurations and ensembles

    CERN Document Server

    Coddington, P; Maynard, C M; Pleiter, D; Yoshié, T

    2007-01-01

    QCDml is an XML-based markup language designed for sharing QCD configurations and ensembles world-wide via the International Lattice Data Grid (ILDG). Based on the latest release, we present key ingredients of the QCDml in order to provide some starting points for colleagues in this community to markup valuable configurations and submit them to the ILDG.

  1. 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.

  2. QCD Thermodynamics with an Improved Lattice Action

    CERN Document Server

    Bernard, C W; DeGrand, T A; Wingate, M; DeTar, C E; Gottlieb, S; Heller, U M; Rummukainen, K; Toussaint, D; Sugar, R L; Bernard, Claude; Hetrick, James E.; Grand, Thomas De; Wingate, Matthew; Tar, Carleton De; Gottlieb, Steven; Heller, Urs M.; Rummukainen, Kari; Toussaint, Doug; Sugar, Robert L.

    1997-01-01

    We have investigated QCD with two flavors of degenerate fermions using a Symanzik-improved lattice action for both the gauge and fermion actions. Our study focuses on the deconfinement transition on an $N_t=4$ lattice. Having located the thermal transition, we performed zero temperature simulations nearby in order to compute hadronic masses and the static quark potential. We find that the present action reduces lattice artifacts present in thermodynamics with the standard Wilson (gauge and fermion) actions. However, it does not bring studies with Wilson-type quarks to the same level as those using the Kogut--Susskind formulation.

  3. Exploring Proton Structure Using Lattice Qcd

    CERN Document Server

    Renner, D B

    2004-01-01

    We calculate moments of the generalized parton distributions of the nucleon using lattice QCD. The generalized parton distributions determine the angular momentum decomposition of the nucleon and the transverse distributions of partons within the nucleon. Additionally, the generalized parton distributions reduce to the elastic form factors and ordinary parton distributions in particular kinematic limits. Thus by calculating moments of the generalized parton distributions in lattice QCD we can explore many facets of the structure of the nucleon. In this effort, we have developed the building block method to determine all the lattice correlation functions which contribute to the off forward matrix elements of the twist two operators. These matrix elements determine the generalized form factors of the nucleon which in turn give the moments of the generalized parton distributions. Thus we use our building block method to calculate all the matrix elements of the lowest twist two operators. Furthermore, we use our ...

  4. Exploring Hyperons and Hypernuclei with Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    S.R. Beane; P.F. Bedaque; A. Parreno; M.J. Savage

    2005-01-01

    In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Lambda's, and Sigma's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P-wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Luscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for Lambda-N scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone, appropriate for lattice calculations, is constructed.

  5. Lattice QCD on Non-Orientable Manifolds

    CERN Document Server

    Mages, Simon; Borsanyi, Szabolcs; Fodor, Zoltan; Katz, Sandor; Szabo, Kalman K

    2015-01-01

    A common problem in lattice QCD simulations on the torus is the extremely long autocorrelation time of the topological charge, when one approaches the continuum limit. The reason is the suppressed tunneling between topological sectors. The problem can be circumvented by replacing the torus with a different manifold, so that the field configuration space becomes connected. This can be achieved by using open boundary conditions on the fields, as proposed earlier. It has the side effect of breaking translational invariance completely. Here we propose to use a non-orientable manifold, and show how to define and simulate lattice QCD on it. We demonstrate in quenched simulations that this leads to a drastic reduction of the autocorrelation time. A feature of the new proposal is, that translational invariance is preserved up to exponentially small corrections. A Dirac-fermion on a non-orientable manifold poses a challenge to numerical simulations: the fermion determinant becomes complex. We propose two approaches to...

  6. Lattice QCD Thermodynamics with Physical Quark Masses

    CERN Document Server

    Soltz, R A; Karsch, F; Mukherjee, Swagato; Vranas, P

    2015-01-01

    Over the past few years new physics methods and algorithms as well as the latest supercomputers have enabled the study of the QCD thermodynamic phase transition using lattice gauge theory numerical simulations with unprecedented control over systematic errors. This is largely a consequence of the ability to perform continuum extrapolations with physical quark masses. Here we review recent progress in lattice QCD thermodynamics, focussing mainly on results that benefit from the use of physical quark masses: the crossover temperature, the equation of state, and fluctuations of the quark number susceptibilities. In addition, we place a special emphasis on calculations that are directly relevant to the study of relativistic heavy ion collisions at RHIC and the LHC.

  7. Lattice QCD spectroscopy for hadronic CP violation

    Directory of Open Access Journals (Sweden)

    Jordy de Vries

    2017-03-01

    In this work we propose a strategy to calculate these couplings by using spectroscopic lattice QCD techniques. Instead of directly calculating the pion–nucleon coupling constants, a challenging task, we use chiral symmetry relations that link the pion–nucleon couplings to nucleon sigma terms and mass splittings that are significantly easier to calculate. In this work, we show that these relations are reliable up to next-to-next-to-leading order in the chiral expansion in both SU(2 and SU(3 chiral perturbation theory. We conclude with a brief discussion about practical details regarding the required lattice QCD calculations and the phenomenological impact of an improved understanding of CP-violating matrix elements.

  8. Neutrinoless double beta decay from lattice QCD

    CERN Document Server

    Nicholson, Amy; Chang, Chia Cheng; Clark, M A; Joo, Balint; Kurth, Thorsten; Rinaldi, Enrico; Tiburzi, Brian; Vranas, Pavlos; Walker-Loud, Andre

    2016-01-01

    While the discovery of non-zero neutrino masses is one of the most important accomplishments by physicists in the past century, it is still unknown how and in what form these masses arise. Lepton number-violating neutrinoless double beta decay is a natural consequence of Majorana neutrinos and many BSM theories, and many experimental efforts are involved in the search for these processes. Understanding how neutrinoless double beta decay would manifest in nuclear environments is key for understanding any observed signals. In these proceedings we present an overview of a set of one- and two-body matrix elements relevant for experimental searches for neutrinoless double beta decay, describe the role of lattice QCD calculations, and present preliminary lattice QCD results.

  9. Eigenspectrum Noise Subtraction Methods in Lattice QCD

    CERN Document Server

    Guerrero, Victor; Wilcox, Walter

    2010-01-01

    We propose a new noise subtraction method, which we call "eigenspectrum subtraction", which uses low eigenmode information to suppress statistical noise at low quark mass. This is useful for lattice calculations involving disconnected loops or all-to-all propagators. It has significant advantages over perturbative subtraction methods. We compare unsubtracted, eigenspectrum and perturbative error bar results for the scalar operator on a small Wilson QCD matrix.

  10. O(a) improved lattice QCD

    OpenAIRE

    Sommer, Rainer

    1997-01-01

    We review the O(a) improvement of lattice QCD with special emphasis on the motivation for performing the improvement programme non-perturbatively and the general concepts of on-shell improvement. The present status of the calculations of various improvement coefficients (perturbative and non-perturbative) is reviewed, as well as the computation of the isospin current normalization constants $Z_A$ and $Z_V$. We comment on recent results for hadronic observables obtained in the improved theory.

  11. Axial Nucleon form factors from lattice QCD

    CERN Document Server

    Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, M

    2010-01-01

    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.

  12. Lattice QCD based on OpenCL

    CERN Document Server

    Bach, Matthias; Philipsen, Owe; Pinke, Christopher

    2012-01-01

    We present an OpenCL-based Lattice QCD application using a heatbath algorithm for the pure gauge case and Wilson fermions in the twisted mass formulation. The implementation is platform independent and can be used on AMD or NVIDIA GPUs, as well as on classical CPUs. On the AMD Radeon HD 5870 our double precision dslash implementation performs at 60 GFLOPS over a wide range of lattice sizes. The hybrid Monte-Carlo presented reaches a speedup of four over the reference code running on a server CPU.

  13. 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.)

  14. Evidence for a bound H-dibaryon from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S R; Detmold, W; Lin, H W; Luu, T C; Orginos, K; Parreno, A; Savage, M J; Torok, A; Walker-Loud, A

    2011-04-01

    We present evidence for the existence of a bound H-dibaryon, an I = 0, J = 0, s = -2 state with valence quark structure uuddss, at a pion mass of m_\\pi < 389 MeV. Extrapolating the results of lattice QCD calculations performed on four ensembles of anisotropic clover gauge-field configurations, with spatial extents of L < 2.0, 2.5, 3.0 and 3.9 fm at a spatial lattice spacing of b_s < 0.123 fm, we find an H-dibaryon bound by B_ ^H = 16.6±2.1±4.6 MeV at a pion mass of m_\\pi < 389 MeV.

  15. FermiQCD A tool kit for parallel lattice QCD applications

    CERN Document Server

    Di Pierro, Massimo

    2002-01-01

    We present here the most recent version of FermiQCD, a collection of C++ classes, functions and parallel algorithms for lattice QCD, based on Matrix Distributed Processing. FermiQCD allows fast development of parallel lattice applications and includes some SSE2 optimizations for clusters of Pentium 4 PCs.

  16. Perfect Actions and Operators for Lattice QCD

    Science.gov (United States)

    Wiese, Uwe-Jens

    1996-05-01

    Wilson's renormalization group implies that lattice actions located on a renormalized trajectory emanating from a fixed point represent perfect discretizations of continuum physics. With a perfect action the spectrum of a lattice theory is identical with the one of the continuum theory even at finite lattice spacing. Similarly, perfect operators yield cut-off independent matrix elements. Hence, continuum QCD can in principle be reconstructed from a lattice with finite spacing. In practice it is difficult to construct perfect actions and perfect operators explicitly. Here perturbation theory is used to derive perfect actions for quarks and gluons by performing a block renormalization group transformation directly from the continuum. The renormalized trajectory for free massive quarks is identified and a parameter in the renormalization group transformation is tuned such that for 1-d configurations the perfect action reduces to the nearest neighbor Wilson fermion action. Then the 4-d perfect action turns out to be extremely local as well, which is vital for numerical simulations. The fixed point action for free gluons is also obtained by blocking from the continuum. For 2-d configurations it reduces to the standard plaquette action, and for 4-d configurations it is still very local. With interactions between quarks and gluons switched on the perfect quark-gluon and 3-gluon vertex functions are computed analytically. In particular, a perfect clover term can be extracted from the quark-gluon vertex. The perturbatively perfect action is directly applicable to heavy quark physics. The construction of a perfect QCD action for light quarks should include nonperturbative effects, which is possible using numerical methods. Classically perfect quark and gluon fields are constructed as well. They allow to interpolate the continuum fields from the lattice data. In this way one can obtain information about space-time regions between lattice points. The classically perfect fields

  17. Dynamics for QCD on an infinite lattice

    CERN Document Server

    Grundling, Hendrik

    2015-01-01

    We prove the existence of the dynamics automorphism group for Hamiltonian QCD on an infinite lattice in R^3, and this is done in a C*-algebraic context. The existence of ground states is also obtained. Starting with the finite lattice model for Hamiltonian QCD developed by Kijowski and Rudolph, we state its field algebra and a natural representation. We then generalize this representation to the infinite lattice, and construct a Hilbert space which has represented on it all the local algebras (i.e. algebras associated with finite connected sublattices) equipped with the correct graded commutation relations. On a suitably large C*-algebra acting on this Hilbert space, and containing all the local algebras, we prove that there is a one parameter automorphism group, which is the pointwise norm limit of the local time evolutions along a sequence of finite sublattices, increasing to the full lattice. This is our global time evolution. We then take as our field algebra the C*-algebra generated by all the orbits of ...

  18. 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.

  19. Spectroscopy of charmed baryons from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Padmanath, M. [Univ. of Graz (Austria). Inst. of Physics; Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Mathur, Nilmani [Tata Institute of Fundamental Research, Bombay (India); Peardon, Michael [Trinity College, Dublin (Ireland)

    2015-01-01

    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. 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) x 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.

  20. Comparing the QCD potential in Perturbative QCD and Lattice QCD at large distances

    CERN Document Server

    Recksiegel, S

    2003-01-01

    We compare the perturbatively calculated QCD potential to that obtained from lattice calculations in the theory without light quark flavours. We examine E_tot(r) = 2 m_pole + V_QCD(r) by re-expressing it in the MSbar mass m = m^MSbar(m^MSbar) and by choosing specific prescriptions for fixing the scale mu (dependent on r and m). By adjusting m so as to maximise the range of convergence, we show that perturbative and lattice calculations agree up to 3 r_0 ~ 7.5 GeV^-1 (r_0 is the Sommer scale) within the perturbative uncertainty of order Lambda^3 r^2.

  1. Doubly heavy baryon spectra guided by lattice QCD

    CERN Document Server

    Garcilazo, H; Vijande, J

    2016-01-01

    This paper provides results for the ground state and excited spectra of three-flavored doubly heavy baryons, $bcn$ and $bcs$. We take advantage of the spin-independent interaction recently obtained to reconcile the lattice SU(3) QCD static potential and the results of nonperturbative lattice QCD for the triply heavy baryon spectra. We show that the spin-dependent potential might be constrained on the basis of nonperturbative lattice QCD results for the spin splittings of three-flavored doubly heavy baryons. Our results may also represent a challenge for future lattice QCD work, because a smaller lattice error could help in distinguishing between different prescriptions for the spin-dependent part of the interaction. Thus, by comparing with the reported baryon spectra obtained with parameters estimated from lattice QCD, one can challenge the precision of lattice calculations. The present work supports a coherent description of singly, doubly and triply heavy baryons with the same Cornell-like interacting poten...

  2. Heavy Dynamical Fermions in Lattice QCD

    CERN Document Server

    Hasenfratz, Anna; Hasenfratz, Anna; Grand, Thomas A. De

    1994-01-01

    It is expected that the only effect of heavy dynamical fermions in QCD is to renormalize the gauge coupling. We derive a simple expression for the shift in the gauge coupling induced by $N_f$ flavors of heavy fermions. We compare this formula to the shift in the gauge coupling at which the confinement-deconfinement phase transition occurs (at fixed lattice size) from numerical simulations as a function of quark mass and $N_f$. We find remarkable agreement with our expression down to a fairly light quark mass. However, simulations with eight heavy flavors and two light flavors show that the eight flavors do more than just shift the gauge coupling. We observe confinement-deconfinement transitions at $\\beta=0$ induced by a large number of heavy quarks. We comment on the relevance of our results to contemporary simulations of QCD which include dynamical fermions.

  3. Combinatorics of Lattice QCD at Strong Coupling

    CERN Document Server

    Unger, Wolfgang

    2014-01-01

    Thermodynamics in the strong coupling limit of lattice QCD has features which may be similar to those of continuum QCD, such as a chiral critical end point and a nuclear liquid gas transition. Here I compare the combinatorics of staggered and Wilson fermions in the strong coupling limit for arbitrary number of colors and flavors. The partition functions can be considered as an expansions in hadronic spatial hoppings from the static limit, where both discretizations can be expressed via formulae with coefficients of distinct combinatorial interpretation. The corresponding multiplicites of hadronic states are evaluated using generalizations of Catalan numbers and Lucas polynomials. I outline how quantum Monte Carlo simulations can be carried out in general, and summarize recent results on the gauge corrections to the strong coupling limit.

  4. Matching Hagedorn mass spectrum with Lattice QCD

    CERN Document Server

    Lo, Pok Man; Redlich, Krzysztof; Sasaki, Chihiro

    2015-01-01

    Based on recent Lattice QCD (LQCD) results obtained at finite temperature, we discuss modeling of the hadronic phase of QCD in the framework of Hadron Resonance Gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges, and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.

  5. Applications Of Chiral Perturbation Theory To Lattice Qcd

    CERN Document Server

    Van de Water, R S

    2005-01-01

    Quantum chromodynamics (QCD) is the fundamental theory that describes the interaction of quarks and gluons. Thus, in principle, one should be able to calculate all properties of hadrons from the QCD Lagrangian. It turns out, however, that such calculations can only be performed numerically on a computer using the nonperturbative method of lattice QCD, in which QCD is simulated on a discrete spacetime grid. Because lattice simulations use unphysically heavy quark masses (for computational reasons), lattice results must be connected to the real world using expressions calculated in chiral perturbation theory (χPT), the low-energy effective theory of QCD. Moreover, because real spacetime is continuous, they must be extrapolated to the continuum using an extension of χPT that includes lattice discretization effects, such as staggered χPT. This thesis is organized as follows. We motivate the need for lattice QCD and present the basic methodology in Chapter 1. We describe a common approximat...

  6. Advances in hadronic structure from Lattice QCD

    Science.gov (United States)

    Constantinou, Martha

    2017-01-01

    Understanding nucleon structure is considered a milestone of hadronic physics and new facilities are planned devoted to its study. A future Electron-Ion-Collider proposed by the scientific community will greatly deepen our knowledge on the fundamental constituents of the visible world. To achieve this goal, a synergy between the experimental and theoretical sectors is imperative, and Lattice QCD is in a unique position to provide input from first principle calculations. In this talk we will discuss recent progress in nucleon structure from Lattice QCD, focusing on the evaluation of matrix elements using state-of-the-art simulations with pion masses at their physical value. The axial form factors, electromagnetic radii, the quark momentum fraction and the spin content of the nucleon will be discussed. We will also highlight quantities that may guide New Physics searches, such as the scalar and tensor charges. Finally, we will give updates on a new direct approach to compute quark parton distributions functions on the lattice.

  7. Charmed bottom baryon spectroscopy from lattice QCD

    CERN Document Server

    Brown, Zachary S; Meinel, Stefan; Orginos, Kostas

    2014-01-01

    We calculate the masses of baryons containing one, two, or three heavy quarks using lattice QCD. We consider all possible combinations of charm and bottom quarks, and compute a total of 36 different states with $J^P = \\frac12^+$ and $J^P = \\frac32^+$. We use domain-wall fermions for the up, down, and strange quarks, a relativistic heavy-quark action for the charm quarks, and nonrelativistic QCD for the bottom quarks. Our analysis includes results from two different lattice spacings and seven different pion masses. We perform extrapolations of the baryon masses to the continuum limit and to the physical pion mass using $SU(4|2)$ heavy-hadron chiral perturbation theory including $1/m_Q$ and finite-volume effects. For the 14 singly heavy baryons that have already been observed, our results agree with the experimental values within the uncertainties. We compare our predictions for the hitherto unobserved states with other lattice calculations and quark-model studies.

  8. 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.

  9. Missing strange resonances in Lattice QCD

    CERN Document Server

    Marczenko, Michał

    2016-01-01

    Recent Lattice QCD (LQCD) studies suggest that there are missing resonances in the strange sector of the Hadron Resonance Gas (HRG) model. By adopting the continuous Hagedorn mass spectrum, we present how different medium compositions influence the HRG predictions of conserved charge fluctuations. It is shown that missing strange resonances may be partially accounted for by applying the Hagedorn mass spectrum extracted from experimentally established hadrons. On the other hand, the strange-baryonic spectra, extracted from LQCD results for fluctuations, are found to be consistent with the unconfirmed states in the Particle Data Group (PDG) database, whilst the strange-mesonic spectrum points towards yet undiscovered states in the intermediate mass region.

  10. Algorithms for Disconnected Diagrams in Lattice QCD

    CERN Document Server

    Gambhir, Arjun Singh; Orginos, Kostas; Yoon, Boram; Gupta, Rajan; Syritsyn, Sergey

    2016-01-01

    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.

  11. 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.)

  12. Pion electric polarizability from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Alexandru, Andrei; Lujan, Michael; Freeman, Walter; Lee, Frank [The George Washington University, 725 21st St. NW, Washington DC, 20052 (United States)

    2016-01-22

    Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. 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 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.

  13. Nuclear correlation functions in lattice QCD

    CERN Document Server

    Detmold, William

    2012-01-01

    We consider the problem of calculating the large number of Wick contractions necessary to compute states with the quantum numbers of many baryons in lattice QCD. We consider a constructive approach and a determinant-based approach and show that these methods allow the required contractions to be performed in computationally manageable amount of time for certain choices of interpolating operators. Examples of correlation functions computed using these techniques are shown for the quantum numbers of the light nuclei, He, Be, C, O and Si.

  14. Charmed Meson Scattering from Lattice QCD

    CERN Document Server

    Moir, Graham

    2016-01-01

    State-of-the-art lattice QCD calculations of scattering amplitudes in coupled-channel $D\\pi$, $D\\eta$ and $D_{s}\\bar{K}$ scattering, as well elastic $DK$ scattering are discussed. The methodology employed allows a determination of the relevant poles in the scattering matrix, while also providing a measure of the coupling of each channel to a given pole. By investigating $S$, $P$ and $D$ wave interactions, the nature of states with $J^{P} = 0^{+}$, relevant for the $D^{*}_{0}(2400)$ and $D^{*}_{s0}(2317)$, as well as states with $J^{P} = 1^{-}, 2^{+}$ are discussed.

  15. Isoscalar meson spectroscopy from lattice QCD

    CERN Document Server

    Dudek, Jozef J; Joo, Balint; Peardon, Michael J; Richards, David G; Thomas, Christopher E

    2011-01-01

    We extract to high statistical precision an excited spectrum of single-particle isoscalar mesons using lattice QCD, including states of high spin and, for the first time, light exotic JPC isoscalars. The use of a novel quark field construction has enabled us to overcome the long-standing challenge of efficiently including quark-annihilation contributions. Hidden-flavor mixing angles are extracted and while most states are found to be close to ideally flavor mixed, there are examples of large mixing in the pseudoscalar and axial sectors in line with experiment. The exotic JPC isoscalar states appear at a mass scale comparable to the exotic isovector states.

  16. Quarkonia at $T>0$ and lattice QCD

    CERN Document Server

    Rothkopf, Alexander

    2016-01-01

    We report here on recent progress in the determination of S-wave and P-wave heavy-quarkonium states at finite temperature. Our results are based on the combination of effective field theories with numerical lattice QCD simulations. These non-perturbative tools allow us to compute the heavy-quarkonium in-medium spectral functions, from which we in turn determine the melting temperatures of individual states and estimate phenomenologically relevant observables, such as the $\\psi^\\prime$ to J/$\\psi$ ratio in heavy-ion collisions.

  17. Even parity excitations of the nucleon in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    B. G. Lasscock; J. N. Hedditch; W. Kamleh; D. B. Leinweber; W. Melnitchouk; A. G. Williams; J. M. Zanotti

    2007-09-01

    We study the spectrum of the even parity excitations of the nucleon in quenched lattice QCD. We extend our earlier analysis by including an expanded basis of nucleon interpolating fields, increasing the physical size of the lattice, including more configurations to enhance statistics and probing closer to the chiral limit. With a review of world lattice data, we conclude that there is little evidence of the Roper resonance in quenched lattice QCD.

  18. Status report on $\\varepsilon_K$ with lattice QCD inputs

    CERN Document Server

    Bailey, Jon A; Leem, Jaehoon; Park, Sungwoo; Jang, Yong-Chull

    2016-01-01

    We report the current status of $\\varepsilon_K$, the indirect CP violation parameter in the neutral kaon system, evaluated using the lattice QCD inputs. We use lattice QCD to fix $\\hat{B}_K$, $\\xi_0$, $\\xi_2$, $|V_{us}|$, $m_c(m_c)$, and $|V_{cb}|$. Since Lattice 2015, FLAG updated $\\hat{B}_K$, exclusive $V_{cb}$ has been updated with new lattice data in the $\\bar{B}\\to D\\ell\

  19. 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 Ds meson decay constant fDs, the strangeness and charmness, the meson mass

  20. Lattice QCD Calculation of Nucleon Structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Keh-Fei; Draper, Terrence

    2016-08-30

    It is emphasized in the 2015 NSAC Long Range Plan [1] 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 rst-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 [2], axial-vector [3], NN [4], and scalar [5] form factors, the quark spin contribution [6] to the proton spin, the strangeness magnetic moment [7], the quark orbital angular momentum [8], the quark momentum fraction [9], and the quark and glue decomposition of the proton momentum and angular momentum [10]. These rst round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical e ects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge con gurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations [11, 12]. 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 [13], charm and strange quark masses, the charmonium spectrum and the Ds meson decay constant fDs [14], the strangeness and charmness [15], the

  1. Exotic Meson Decay Widths using Lattice QCD

    CERN Document Server

    Cook, M S

    2006-01-01

    A decay width calculation for a hybrid exotic meson h, with JPC=1-+, is presented for the channel h->pi+a1. This quenched lattice QCD simulation employs Luescher's finite box method. Operators coupling to the h and pi+a1 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 pi+a1 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.

  2. 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.

  3. 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 at⁻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.

  4. Dynamics for QCD on an Infinite Lattice

    Science.gov (United States)

    Grundling, Hendrik; Rudolph, Gerd

    2017-02-01

    We prove the existence of the dynamics automorphism group for Hamiltonian QCD on an infinite lattice in R^3, and this is done in a C*-algebraic context. The existence of ground states is also obtained. Starting with the finite lattice model for Hamiltonian QCD developed by Kijowski, Rudolph (cf. J Math Phys 43:1796-1808 [15], J Math Phys 46:032303 [16]), we state its field algebra and a natural representation. We then generalize this representation to the infinite lattice, and construct a Hilbert space which has represented on it all the local algebras (i.e., kinematics algebras associated with finite connected sublattices) equipped with the correct graded commutation relations. On a suitably large C*-algebra acting on this Hilbert space, and containing all the local algebras, we prove that there is a one parameter automorphism group, which is the pointwise norm limit of the local time evolutions along a sequence of finite sublattices, increasing to the full lattice. This is our global time evolution. We then take as our field algebra the C*-algebra generated by all the orbits of the local algebras w.r.t. the global time evolution. Thus the time evolution creates the field algebra. The time evolution is strongly continuous on this choice of field algebra, though not on the original larger C*-algebra. We define the gauge transformations, explain how to enforce the Gauss law constraint, show that the dynamics automorphism group descends to the algebra of physical observables and prove that gauge invariant ground states exist.

  5. Connecting physical resonant amplitudes and lattice QCD

    CERN Document Server

    Bolton, Daniel R; Wilson, David J

    2015-01-01

    We present a determination of the isovector, $P$-wave $\\pi\\pi$ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using $m_\\pi =236$ MeV. The finite volume spectra are described using extensions of L\\"uscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at $m_\\pi= 140$ MeV. The scattering phase shift is found to be in good agreement with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a $\\rho$-resonance pole at $E_\\rho= \\left[755(2)(1)(^{20}_{02})-\\frac{i}{2}\\,129(3)(1)(^{7}_{1})\\right]~{\\rm MeV}$. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.

  6. Phase diagram of twisted mass lattice QCD

    Science.gov (United States)

    Sharpe, Stephen R.; Wu, Jackson M.

    2004-11-01

    We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m2π/(4πfπ)2˜aΛ (a being the lattice spacing, and Λ=ΛQCD). We then focus on the region where m2π/(4πfπ)2˜(aΛ)2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is nonvanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transition extends into the twisted mass plane, ending with two symmetrical second order points at which the mass of the neutral pion vanishes. We provide graphs of the condensate and pion masses for both scenarios, and note a simple mathematical relation between them. These results may be of importance to numerical simulations.

  7. Lattice QCD spectroscopy for hadronic CP violation

    Science.gov (United States)

    de Vries, Jordy; Mereghetti, Emanuele; Seng, Chien-Yeah; Walker-Loud, André

    2017-03-01

    The interpretation of nuclear electric dipole moment (EDM) experiments is clouded by large theoretical uncertainties associated with nonperturbative matrix elements. In various beyond-the-Standard Model scenarios nuclear and diamagnetic atomic EDMs are expected to be dominated by CP-violating pion-nucleon interactions that arise from quark chromo-electric dipole moments. The corresponding CP-violating pion-nucleon coupling strengths are, however, poorly known. In this work we propose a strategy to calculate these couplings by using spectroscopic lattice QCD techniques. Instead of directly calculating the pion-nucleon coupling constants, a challenging task, we use chiral symmetry relations that link the pion-nucleon couplings to nucleon sigma terms and mass splittings that are significantly easier to calculate. In this work, we show that these relations are reliable up to next-to-next-to-leading order in the chiral expansion in both SU (2) and SU (3) chiral perturbation theory. We conclude with a brief discussion about practical details regarding the required lattice QCD calculations and the phenomenological impact of an improved understanding of CP-violating matrix elements.

  8. Spin-Orbit Force from Lattice QCD

    CERN Document Server

    Murano, K; Aoki, S; Doi, T; Hatsuda, T; Ikeda, Y; Inoue, T; Nemura, H; Sasaki, K

    2013-01-01

    We present a first attempt to determine nucleon-nucleon potentials in the parity-odd sector, which appear in 1P1, 3P0, 3P1, 3P2-3F2 channels, in Nf=2 lattice QCD simulations. These potentials are constructed from the Nambu-Bethe-Salpeter wave functions for J^P=0^-, 1^- and 2^-, which correspond to A1^-, T1^- and T2^- + E^- representation of the cubic group, respectively. We have found a large and attractive spin-orbit potential VLS(r) in the isospin-triplet channel, which is qualitatively consistent with the phenomenological determination from the experimental scattering phase shifts. The potentials obtained from lattice QCD are used to calculate the scattering phase shifts in 1P1, 3P0, 3P1 and 3P2-3F2 channels. The strong attractive spin-orbit force and a weak repulsive central force in spin-triplet P-wave channels lead to an attraction in the 3P2 channel, which is related to the P-wave neutron paring in neutron stars.

  9. The CKM matrix and flavor physics from lattice QCD

    CERN Document Server

    Van de Water, Ruth S

    2009-01-01

    I discuss the role of lattice QCD in testing the Standard Model and searching for physics beyond the Standard Model in the quark flavor sector. I first review the Standard Model CKM framework. I then present the current status of the CKM matrix, focusing on determinations of CKM matrix elements and constraints on the CKM unitarity triangle that rely on lattice QCD calculations of weak matrix elements. I also show the potential impact of improved lattice QCD calculations on the global CKM unitarity triangle fit. I then describe several hints of new physics in the quark flavor sector that rely on lattice QCD calculations of weak matrix elements, such as evidence of a ~2-3 sigma tension in the CKM unitarity triangle and the "f_{D_s} puzzle". I finish with a discussion of lattice QCD calculations of rare B- and K-decays needed to probe physics beyond the Standard Model at future experiments.

  10. Current status of $\\varepsilon_K$ in lattice QCD

    CERN Document Server

    Lee, Weonjong

    2016-01-01

    We present the current status of $\\varepsilon_K$ evaluated directly from the standard model using lattice QCD inputs. The lattice QCD inputs include $\\hat{B}_K$, $\\xi_0$, $\\xi_2$, $|V_{us}|$, $m_c(m_c)$, and $|V_{cb}|$. Recently, FLAG has updated $\\hat{B}_K$, exclusive $|V_{cb}|$ has been updated with new lattice data in the $\\bar{B}\\to D\\ell\\bar{\

  11. Lattice-motivated holomorphic nearly perturbative QCD

    CERN Document Server

    Ayala, Cesar; Kogerler, Reinhart

    2016-01-01

    Newer lattice results indicate that, in the Landau gauge at low spacelike momenta, the gluon propagator and the ghost dressing function are finite nonzero. This leads to a definition of the QCD running coupling, in a specific scheme, that goes to zero at low spacelike momenta. We construct a running coupling which fulfills these conditions, and at the same time reproduces to a high precision the perturbative behavior at high momenta. The coupling is constructed in such a way that it reflects qualitatively correctly the holomorphic (analytic) behavior of spacelike observables in the complex plane of the squared momenta, as dictated by the general principles of Quantum Field Theories. Further, we require the coupling to reproduce correctly the nonstrange semihadronic decay rate of tau lepton which is the best measured low-momentum QCD observable with negligible higher-twist effects. Subsequent application of the Borel sum rules to the V+A spectral functions of tau lepton decays, as measured by OPAL Collaboratio...

  12. Thermodynamics of strong-interaction matter from Lattice QCD

    CERN Document Server

    Ding, Heng-Tong; Mukherjee, Swagato

    2015-01-01

    We review results from lattice QCD calculations on the thermodynamics of strong-interaction matter with emphasis on input these calculations can provide to the exploration of the phase diagram and properties of hot and dense matter created in heavy ion experiments. This review is organized as follows: 1) Introduction, 2) QCD thermodynamics on the lattice, 3) QCD phase diagram at high temperature, 4) Bulk thermodynamics, 5) Fluctuations of conserved charges, 6) Transport properties, 7) Open heavy flavors and heavy quarkonia, 8) QCD in external magnetic fields, 9) Summary.

  13. Charmonium properties in hot quenched lattice QCD

    CERN Document Server

    Ding, H -T; Kaczmarek, O; Karsch, F; Satz, H; Soeldner, W

    2012-01-01

    We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both S wave states ($J/\\psi$ and $\\eta_c$) and P wave states ($\\chi_{c0}$ and $\\chi_{c1}$) disappear already at about $1.5 T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/\\pi T$ at $1.5 T_c\\lesssim T\\lesssim 3 T_c$.

  14. Charmonium properties in hot quenched lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Ding, H. -T.; Francis, A.; Kaczmarek, O.; Karsch, F.; Satz, H.; Soeldner, W.

    2012-07-01

    We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that both S wave states (J/ψ and ηc) and P wave states (χc0 and χc1) disappear already at about 1.5Tc. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below Tc and approximately 1/πT at 1.5Tc≲T≲3Tc.

  15. Nuclear Parity Violation from Lattice QCD

    CERN Document Server

    Kurth, Thorsten; Rinaldi, Enrico; Vranas, Pavlos; Nicholson, Amy; Strother, Mark; Walker-Loud, Andre

    2015-01-01

    The electroweak interaction at the level of quarks and gluons are well understood from precision measurements in high energy collider experiments. Relating these fundamental parameters to Hadronic Parity Violation in nuclei however remains an outstanding theoretical challenge. One of the most interesting observables in this respect is the parity violating hadronic neutral current: it is hard to measure in collider experiments and is thus the least constrained observable of the Standard Model. Precision measurements of parity violating transitions in nuclei can help to improve these constraints. In these systems however, the weak interaction is masked by effects of the seven orders of magnitude stronger non-perturbative strong interaction. Therefore, in order to relate experimental measurements of the parity violating pion-nucleon couplings to the fundamental Lagrangian of the SM, these non-perturbative effects have to be well understood. In this paper, we are going to present a Lattice QCD approach for comput...

  16. Spin–orbit force from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Murano, K. [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Ishii, N. [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Aoki, S. [Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Doi, T. [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Hatsuda, T. [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Kavli IPMU, The University of Tokyo, Kashiwa 277-8583 (Japan); Ikeda, Y. [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Inoue, T. [Nihon University, College of Bioresource Sciences, Kanagawa 252-0880 (Japan); Nemura, H.; Sasaki, K. [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan)

    2014-07-30

    We present a first attempt to determine nucleon–nucleon potentials in the parity-odd sector, which appear in the {sup 1}P{sub 1}, {sup 3}P{sub 0}, {sup 3}P{sub 1}, {sup 3}P{sub 2}–{sup 3}F{sub 2} channels, in N{sub f}=2 lattice QCD simulations. These potentials are constructed from the Nambu–Bethe–Salpeter wave functions for J{sup P}=0{sup −},1{sup −} and 2{sup −}, which correspond to the A{sub 1}{sup −}, T{sub 1}{sup −} and T{sub 2}{sup −}⊕E{sup −} representation of the cubic group, respectively. We have found a large and attractive spin–orbit potential V{sub LS}(r) in the isospin-triplet channel, which is qualitatively consistent with the phenomenological determination from the experimental scattering phase shifts. The potentials obtained from lattice QCD are used to calculate the scattering phase shifts in the {sup 1}P{sub 1}, {sup 3}P{sub 0}, {sup 3}P{sub 1} and {sup 3}P{sub 2}–{sup 3}F{sub 2} channels. The strong attractive spin–orbit force and a weak repulsive central force in spin-triplet P-wave channels lead to an attraction in the {sup 3}P{sub 2} channel, which is related to the P-wave neutron paring in neutron stars.

  17. Topics in Effective Field Theory for Lattice QCD

    CERN Document Server

    Walker-Loud, A

    2006-01-01

    In this work, we extend and apply effective field theory techniques to systematically understand a subset of lattice artifacts which pollute the lattice correlation functions for a few processes of physical interest. Where possible, we compare to existing lattice QCD calculations. In particular, we extend the heavy baryon Lagrangian to the next order in partially quenched chiral perturbation theory and use it to compute the masses of the lightest spin-1/2 and spin-3/2 baryons to next-to-next-to leading order. We then construct the twisted mass chiral Lagrangian for baryons and apply it to compute the lattice spacing corrections to the baryon masses simulated with twisted mass lattice QCD. We extend computations of the nucleon electromagnetic structure to account for finite volume effects, as these observables are particularly sensitive to the finite extent of the lattice. We resolve subtle peculiarities for lattice QCD simulations of polarizabilities and we show that using background field techniques, one can...

  18. Lattice QCD for Baryon Rich Matter - Beyond Taylor Expansions

    Science.gov (United States)

    Bornyakov, V.; Boyda, D.; Goy, V.; Molochkov, A.; Nakamura, A.; Nikolaev, A.; Zakharov, V. I.

    2016-12-01

    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.

  19. Introductory lectures on lattice QCD at nonzero baryon number

    Science.gov (United States)

    Aarts, Gert

    2016-04-01

    These lecture notes contain an elementary introduction to lattice QCD at nonzero chemical potential. Topics discussed include chemical potential in the continuum and on the lattice; the sign, overlap and Silver Blaze problems; the phase boundary at small chemical potential; imaginary chemical potential; and complex Langevin dynamics. An incomplete overview of other approaches is presented as well. These lectures are meant for postgraduate students and postdocs with an interest in extreme QCD. A basic knowledge of lattice QCD is assumed but not essential. Some exercises are included at the end.

  20. Introductory lectures on lattice QCD at nonzero baryon number

    CERN Document Server

    Aarts, Gert

    2015-01-01

    These lecture notes contain an elementary introduction to lattice QCD at nonzero chemical potential. Topics discussed include chemical potential in the continuum and on the lattice; the sign, overlap and Silver Blaze problems; the phase boundary at small chemical potential; imaginary chemical potential; and complex Langevin dynamics. An incomplete overview of other approaches is presented as well. These lectures are meant for postgraduate students and postdocs with an interest in extreme QCD. A basic knowledge of lattice QCD is assumed but not essential. Some exercises are included at the end.

  1. Nucleon Structure in Lattice QCD using twisted mass fermions

    CERN Document Server

    Alexandrou, C; Korzec, T; Carbonell, J; Harraud, P A; Papinutto, M; Guichon, P; Jansen, K

    2010-01-01

    We present results on the nucleon form factors and moments of generalized parton distributions obtained within the twisted mass formulation of lattice QCD. We include a discussion of lattice artifacts by examining results at different volumes and lattice spacings. We compare our results with those obtained using different discretization schemes and to experiment.

  2. Equation of state and more from lattice regularized QCD

    CERN Document Server

    Karsch, Frithjof

    2008-01-01

    We present results from a calculation of the QCD equation of state with two light (up, down) and one heavier (strange) quark mass performed on lattices with three different values of the lattice cut-off. We show that also on the finest lattice analyzed by us observables sensitive to deconfinement and chiral symmetry restoration, respectively, vary most rapidly in the same temperature regime.

  3. Hadro-quarkonium from Lattice QCD

    CERN Document Server

    Alberti, Maurizio; Collins, Sara; Knechtli, Francesco; Moir, Graham; Söldner, Wolfgang

    2016-01-01

    The hadro-quarkonium picture provides one possible interpretation for the pentaquark candidates with hidden charm, recently reported by the LHCb Collaboration, as well as for some of the charmonium-like X,Y,Z states. In this model, a heavy quarkonium core resides within a light hadron giving rise to four- and five-quark/antiquark bound states. We test this scenario in the heavy quark limit by investigating the modification of the potential between a static quark-antiquark pair induced by the presence of a hadron. Our lattice QCD simulations are performed on a CLS ensemble with $N_f=2+1$ flavours of non-perturbatively improved Wilson quarks at a pion mass of about 223 MeV and a lattice spacing of about $a=0.0854$ fm. We study the static potential in the presence of a variety of light mesons as well as of octet and decuplet baryons. In all these cases, the resulting configurations are favoured energetically, however, the associated binding energies between the quarkonium in the heavy quark limit and the light h...

  4. Formal Developments for Lattice QCD with Applications to Hadronic Systems

    CERN Document Server

    Davoudi, Zohreh

    2014-01-01

    Lattice quantum chromodynamics (QCD) will soon become the primary theoretical tool in rigorous studies of single- and multi-hadron sectors of QCD. It is truly ab initio meaning that its only parameters are those of standard model. The result of a lattice QCD calculation corresponds to that of nature only in the limit when the volume of spacetime is taken to infinity and the spacing between discretized points on the lattice is taken to zero. A better understanding of these discretization and volume effects not only provides the connection to the infinite-volume continuum observables, but also leads to optimized calculations that can be performed with available computational resources. This thesis includes various formal developments in this direction, along with proposals for improvements, to be applied to the upcoming lattice QCD studies of nuclear and hadronic systems. Among these developments are i) an analytical investigation of the recovery of rotational symmetry with the use of suitably-formed smeared op...

  5. Effective potential for Polyakov loops in lattice QCD

    Science.gov (United States)

    Nemoto, Y.; RBC Collaboration

    2003-05-01

    Toward the derivation of an effective theory for Polyakov loops in lattice QCD, we examine Polyakov loop correlation functions using the multi-level algorithm which was recently developed by Luscher and Weisz.

  6. Lattice QCD results at finite T and \\mu

    CERN Document Server

    Fodor, Z

    2002-01-01

    We propose a method to study lattice QCD at finite temperature (T) and chemical potential (\\mu). We test the method and compare it with the Glasgow method using n_f=4 staggered QCD with imaginary \\mu. The critical endpoint (E) of QCD on the Re(\\mu)-T plane is located. We use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. Our results are based on {\\cal{O}}(10^3-10^4) configurations.

  7. The finite volume spectrum of excited states from lattice QCD simulations

    CERN Document Server

    Bulava, John; Jhang, You-Cyuan; Lenkner, David; Morningstar, Colin J; Foley, Justin; Juge, Keisuke J; Wong, Chik Him

    2014-01-01

    We present results for the spectrum of excited mesons obtained from temporal correlations of spatially-extended single-hadron and multi-hadron operators computed in lattice QCD. The stochastic LapH algorithm is implemented on anisotropic, dynamical lattices for isovectors for pions of mass $390$ MeV. A large correlation matrix with single-particle and two-particle probe operators is diagonalized to identify resonances. The masses of excited states in the $I=1, S=0, T_{1u}^+$ channel as well as the mixing of single and multi-particle probe operators are presented.

  8. Lattice Study of Anisotropic QED-3

    CERN Document Server

    Hands, S; Hands, Simon; Thomas, Iorwerth Owain

    2004-01-01

    We present results from a Monte Carlo simulation of non-compact lattice QED in 3 dimensions on a $16^3$ lattice in which an explicit anisotropy between $x$ and $y$ hopping terms has been introduced into the action. This formulation is inspired by recent formulations of anisotropic QED$_3$ as an effective theory of the non-superconducting portion of the cuprate phase diagram, with relativistic fermion degrees of freedom defined near the nodes of the gap function on the Fermi surface, and massless photon degrees of freedom reproducing the dynamics of the phase disorder of the superconducting order parameter. Using a parameter set corresponding to broken chiral symmetry in the isotropic limit, our results show that the renormalised anisotropy, defined in terms of the ratio of correlation lengths of gauge invariant bound states in the $x$ and $y$ directions, exceeds the explicit anisotropy $\\kappa$ introduced in the lattice action, implying in contrast to recent analytic results that anisotropy is a relevant defo...

  9. Topics in effective field theory as applied to lattice QCD

    Science.gov (United States)

    Smigielski, Brian

    This thesis focuses on understanding aspects of hadronic physics using numerical and analytic computations which comprise the research fields of Lattice QCD and Effective Field Theories. Lattice QCD is a numerical approximation to QCD that is computed within a finite spacetime volume, a finite lattice spacing, and unphysically large values of the quark mass used to limit computational run time. Because Lattice QCD calculations are implemented with these constraints, it becomes necessary to understand how these constraints influence the physics if we are to extract physical observables. This requires the use and matching of an effective field theory for mesons and baryons which are the fundamental degrees of freedom of the effective field theory Lagrangian. We consider pion and nucleon interactions in Chapter 3 when computational demands force the use of small, spacetime lattices, and extract the axial charge of the nucleon. In Chapters 4 and 5 we examine systems of up to twelve particles of single species, pions or kaons, and mixed species systems of pions and kaons. From these systems we learn about the scattering lengths and three-body forces of these particles. These multi-particle systems also allow one to understand the behavior of finite density systems on the lattice. Lastly in Chapter 6, we examine parton distributions of the pion for a nonzero change in the pion's momentum. These are known as generalized parton distributions and reveal information regarding the valence quarks within a particular hadron. Before the advent of QCD, however, these particles were also known as partons.

  10. Search for the pentaquark resonance signature in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    B. G. Lasscock; J. Hedditch; D. B. Leinweber; W. Melnitchouk; A. W. Thomas; A. G. Williams; R. D. Young; J. M. Zanotti

    2005-03-01

    Claims concerning the possible discovery of the $\\Theta^+$ pentaquark, with minimal quark content $uudd\\bar{s}$, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large $20^{3} \\times 40$ lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquark states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD.

  11. Numerical techniques for lattice QCD in the $\\epsilon$--regime

    OpenAIRE

    Giusti, L; Hoelbling, C.; Lüscher, M.; Wittig, H.

    2002-01-01

    In lattice QCD it is possible, in principle, to determine the parameters in the effective chiral lagrangian (including weak interaction couplings) by performing numerical simulations in the $\\epsilon$--regime, i.e. at quark masses where the physical extent of the lattice is much smaller than the Compton wave length of the pion. The use of a formulation of the lattice theory that preserves chiral symmetry is attractive in this context, but the numerical implementation of any such approach requ...

  12. Magnetic fields in QCD vacuum: A lattice view

    Energy Technology Data Exchange (ETDEWEB)

    Buividovich, P.V. [Regensburg University, Institute for Theoretical Physics, Regensburg (Germany)

    2016-08-15

    We review the basic phenomena in QCD subject to strong magnetic fields which are accessible in experiment and can be also studied in lattice QCD simulations: enhanced fluctuations of electric current and electric dipole moment, the negative magnetoresistivity and the inverse magnetic catalysis. We comment on the possibility of experimental detection of negative magnetoresistivity by analysing the angular distributions of dilepton pairs in off-central heavy-ion collisions. (orig.)

  13. Exploring the Spectrum of QCD Using the Lattice

    Energy Technology Data Exchange (ETDEWEB)

    Bulava, John; Dudek, Jozef; Edwards, Robert; Engelson, Eric; Foley, Justin; Joo, Balint; Juge, Jimmy; Lin, Huey-Wen; Mathur, Nilmani; Morningstar, Colin; Peardon, Mike; Richards, David; Ryan, Sinead; Thomas, Christopher; Thomas, Anthony

    2009-08-01

    The calculation of the spectrum of QCD is key to an understanding of the strong interactions, and vital if we are to capitalize on the experimental study of the spectrum. In this paper, we describe progress towards understanding the spectrum of resonances of both mesons and baryons from lattice QCD, focusing in particular on the resonances of the $I=1/2$ nucleon states, and of charmonium mesons composed of the heavy charmed quarks.

  14. Magnetic fields in QCD vacuum: A lattice view

    Science.gov (United States)

    Buividovich, P. V.

    2016-08-01

    We review the basic phenomena in QCD subject to strong magnetic fields which are accessible in experiment and can be also studied in lattice QCD simulations: enhanced fluctuations of electric current and electric dipole moment, the negative magnetoresistivity and the inverse magnetic catalysis. We comment on the possibility of experimental detection of negative magnetoresistivity by analysing the angular distributions of dilepton pairs in off-central heavy-ion collisions.

  15. Do lattice data constrain the vector interaction strength of QCD?

    Directory of Open Access Journals (Sweden)

    Jan Steinheimer

    2014-09-01

    Full Text Available We show how repulsive interactions of deconfined quarks as well as confined hadrons have an influence on the baryon number susceptibilities and the curvature of the chiral pseudo-critical line in effective models of QCD. We discuss implications and constraints for the vector interaction strength from comparisons to lattice QCD and comment on earlier constraints, extracted from the curvature of the transition line of QCD and compact star observables. Our results clearly point to a strong vector repulsion in the hadronic phase and near-zero repulsion in the deconfined phase.

  16. Opportunities, Challenges, and Fantasies in Lattice QCD

    CERN Document Server

    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.

  17. Lattice QCD - A guide for people who want results

    CERN Document Server

    Davies, C

    2005-01-01

    Lattice QCD was invented thirty years ago but only in the last few years has it finally fulfilled its promise as a precision tool for calculations in hadron physics. This review will cover the fundamentals of discretising QCD onto a space-time lattice and how to reduce the errors associated with the discretisation. This 'improvement' is the key that has made the enormous computational task of a lattice QCD calculation tractable and enabled us to reach the recent milestone of precision calculations of simple 'gold-plated' hadron masses. Accurate decay matrix elements, such as those for leptonic and semileptonic decays of heavy mesons needed by the B factory experimental programme, are now within sight. I will describe what goes into such calculations and what the future prospects and limitations are.

  18. Renormalization of operators for excited-state hadrons in lattice QCD.

    Energy Technology Data Exchange (ETDEWEB)

    Ekaterina Mastropas, David Richards

    2012-04-01

    One of the primary aims of lattice QCD is to accurately compute the spectrum of hadronic excitations from first principles. However, obtaining an accurate resolution of excited states using methods of lattice QCD is not a trivial problem due to faster decay of excited-states correlation functions in Euclidean space in comparison to those of ground states. To overcome this difficulty, anisotropic lattices with a finer temporal discretization are used. To go beyond the spectrum, in order to study the properties of the states, one needs to compute corresponding matrix elements. Thus, for example, the quark distribution amplitudes in mesons are given by matrix elements of quark bilinear operators, while in baryons, the corresponding quark distribution amplitudes are related to matrix elements of three-quark operators. To relate the matrix elements calculated on the lattice to those in the continuum, and hence to relate to the measured experimentally, it is necessary to evaluate matching coefficients. In this work we describe the calculation of the matching coefficients using perturbation theory for the improved anisotropic-clover fermion action used for our studies of excited states.

  19. 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.

  20. Electric polarizability of neutral hadrons from lattice QCD

    Science.gov (United States)

    Lee, Frank; Alexandru, Andrei; Lujan, Michael; Freeman, Walter

    2017-01-01

    We report on the electric polarizability for the neutron, neutral pion, and neutral kaon from lattice QCD. The results are based on dynamical QCD ensembles at two different pion masses: 306 and 227 MeV. An infinite volume extrapolation is performed for each hadron at both pion masses. The resulting polarizabilities are compared with other lattice calculations, ChPT, and experiment. This work is supported in part by the NSF CAREER grant PHY-1151648, the U.S. Department of Energy grant DE-FG02-95ER40907, and the ARCS foundation.

  1. Equivalent of a Thouless energy in lattice QCD Dirac spectra

    CERN Document Server

    Berbenni-Bitsch, M E; Ma, J Z; Meyer, S; Wilke, T

    2000-01-01

    Random matrix theory (RMT) is a powerful statistical tool to model spectral fluctuations. In addition, RMT provides efficient means to separate different scales in spectra. Recently RMT has found application in quantum chromodynamics (QCD). In mesoscopic physics, the Thouless energy sets the universal scale for which RMT applies. We try to identify the equivalent of a Thouless energy in complete spectra of the QCD Dirac operator with staggered fermions and $SU_c(2)$ lattice gauge fields. Comparing lattice data with RMT predictions we find deviations which allow us to give an estimate for this scale.

  2. Properties of the quark gluon plasma from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Mages, Simon Wolfgang

    2015-03-02

    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.

  3. Further Precise Determinations of $\\alpha_s$ from Lattice QCD

    CERN Document Server

    Davies, C T H; Lepage, G P; McCallum, P; Shigemitsu, J; Sloan, J

    1997-01-01

    We present a new determination of the strong coupling constant from lattice QCD simulations. We use four different short-distance quantities to obtain the coupling, three different (infrared) meson splittings to tune the simulation parameters, and a wide range of lattice spacings, quark masses, and lattice volumes to test for systematic errors. Our final result consists of ten different determinations of $\\alpha^{(3)}_{P}(8.2 GeV)$, which agree well with each other and with our previous results. The most accurate of these, when evolved perturbatively to the $Z^0$ mass, gives obtained from other recent lattice simulations.

  4. Testing chiral effective theory with quenched lattice QCD

    CERN Document Server

    Giusti, Leonardo; Necco, S; Peña, C; Wennekers, J; Wittig, H

    2008-01-01

    We investigate two-point correlation functions of left-handed currents computed in quenched lattice QCD with the Neuberger-Dirac operator. We consider two lattice spacings a~0.09,0.12 fm and two different lattice extents L~ 1.5, 2.0 fm; quark masses span both the p- and the epsilon-regimes. We compare the results with the predictions of quenched chiral perturbation theory, with the purpose of testing to what extent the effective theory reproduces quenched QCD at low energy. In the p-regime we test volume and quark mass dependence of the pseudoscalar decay constant and mass; in the epsilon-regime, we investigate volume and topology dependence of the correlators. While the leading order behaviour predicted by the effective theory is very well reproduced by the lattice data in the range of parameters that we explored, our numerical data are not precise enough to test next-to-leading order effects.

  5. Nucleon-Nucleon Scattering From Fully-Dynamical Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Konstantinos Orginos; Martin Savage; Paulo Bedaque; Silas Beane

    2006-07-01

    We present results of the first fully-dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1 S0 channel and 3 S1 - 3 D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions

  6. The Additional Interpolators Method for Variational Analysis in Lattice QCD

    CERN Document Server

    Schiel, Rainer W

    2015-01-01

    In this paper, I describe the Additional Interpolators Method, a new technique for variational analysis in lattice QCD. It is shown to be an excellent method which uses additional interpolators to remove backward in time running states that would otherwise contaminate the signal. The proof of principle, which also makes use of the Time-Shift Trick (Generalized Pencil-of-Functions method), will be delivered at an example on a $64^4$ lattice close to the physical pion mass.

  7. A scalable PC-based parallel computer for lattice QCD

    CERN Document Server

    Fodor, Z; Papp, G

    2002-01-01

    A PC-based parallel computer for medium/large scale lattice QCD simulations is suggested. The Eotvos 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.

  8. Comparing Clusters and Supercomputers for Lattice QCD

    CERN Document Server

    Gottlieb, S

    2001-01-01

    Since the development of the Beowulf project to build a parallel computer from commodity PC components, there have been many such clusters built. The MILC QCD code has been run on a variety of clusters and supercomputers. Key design features are identified, and the cost effectiveness of clusters and supercomputers are compared.

  9. Evidence for hard chiral logarithms in quenched lattice QCD

    CERN Document Server

    Kim, S; Kim, Seyong; Sinclair, D K

    1995-01-01

    We present the first direct evidence that quenched QCD differs from full QCD in the chiral (m_q \\rightarrow 0) limit, as predicted by chiral perturbation theory, from our quenched lattice QCD simulations at \\beta = 6/g^2 = 6.0. We measured the spectrum of light hadrons on 16^3 \\times 64, 24^3 \\times 64 and 32^3 \\times 64, using staggered quarks of masses m_q=0.01, m_q=0.005 and m_q=0.0025. The pion masses showed clear evidence for logarithmic violations of the PCAC relation m_{\\pi}^2 \\propto m_q, as predicted by quenched chiral perturbation theory. The dependence on spatial lattice volume precludes this being a finite size effect. No evidence was seen for such chiral logarithms in the behaviour of the chiral condensate \\langle\\bar{\\psi}\\psi\\rangle.

  10. Lattice QCD Results at Finite Temperature and Density

    CERN Document Server

    Fodor, Z

    2003-01-01

    Recent lattice results on QCD at finite temperatures and densities are reviewed. Two new and independent techniques give compatible results for physical quantities. The phase line separating the hadronic and quark-gluon plasma phases, the critical endpoint and the equation of state are discussed.

  11. The QCD equation of state at nonzero densities lattice result

    CERN Document Server

    Fodor, Z; Szabó, K K

    2003-01-01

    In this letter we give the equation of state of QCD at finite temperatures and densities. The recently proposed overlap improving multi-parameter reweighting technique is used to determine observables at nonvanishing chemical potentials. Our results are obtained by studying n_f=2+1 dynamical staggered quarks with semi-realistic masses on N_t=4 lattices.

  12. What can Lattice QCD theorists learn from NMR spectroscopists?

    CERN Document Server

    Fleming, George T

    2004-01-01

    Euclidean-time hadron correlation functions computed in Lattice QCD (LQCD) are modeled by a sum of decaying exponentials, reminiscent of the exponentially damped sinusoid models of free induction decay (FID) in Nuclear Magnetic Resonance (NMR) spectroscopy. We present our initial progress in studying how data modeling techniques commonly used in NMR perform when applied to LQCD data.

  13. Nonperturbative Renormalisation of Composite Operators in Lattice QCD

    CERN Document Server

    Göckeler, M; Oelrich, H; Perlt, H; Petters, D; Rakow, P; Schäfer, A; Schierholz, G; Schiller, A

    1999-01-01

    We investigate the nonperturbative renormalisation of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields. These include operators which are relevant to the calculation of moments of hadronic structure functions. The computations are based on Monte Carlo simulations using quenched Wilson fermions.

  14. The I=2 pipi S-wave Scattering Phase Shift from Lattice QCD

    OpenAIRE

    Beane, S. R.; Chang, E.; Detmold, W.; Lin, H. W.; Luu, T. C.; Orginos, K.; Parreno, A.; Savage, M. J.; A. Torok; Walker-Loud, A.

    2011-01-01

    The pi+pi+ s-wave scattering phase-shift is determined below the inelastic threshold using Lattice QCD. Calculations were performed at a pion mass of m_pi~390 MeV with an anisotropic n_f=2+1 clover fermion discretization in four lattice volumes, with spatial extent L~2.0, 2.5, 3.0 and 3.9 fm, and with a lattice spacing of b_s~0.123 fm in the spatial direction and b_t b_s/3.5 in the time direction. The phase-shift is determined from the energy-eigenvalues of pi+pi+ systems with both zero and n...

  15. The I=2 pipi S-wave Scattering Phase Shift from Lattice QCD

    CERN Document Server

    Beane, S R; Detmold, W; Lin, H W; Luu, T C; Orginos, K; Parreno, A; Savage, M J; Torok, A; Walker-Loud, A

    2011-01-01

    The pi+pi+ s-wave scattering phase-shift is determined below the inelastic threshold using Lattice QCD. Calculations were performed at a pion mass of m_pi~390 MeV with an anisotropic n_f=2+1 clover fermion discretization in four lattice volumes, with spatial extent L~2.0, 2.5, 3.0 and 3.9 fm, and with a lattice spacing of b_s~0.123 fm in the spatial direction and b_t b_s/3.5 in the time direction. The phase-shift is determined from the energy-eigenvalues of pi+pi+ systems with both zero and non-zero total momentum in the lattice volume using Luscher's method. Our calculations are precise enough to allow for a determination of the threshold scattering parameters, the scattering length a, the effective range r, and the shape-parameter P, in this channel and to examine the prediction of two-flavor chiral perturbation theory: m_pi^2 a r = 3+O(m_pi^2/Lambda_chi^2). Chiral perturbation theory is used, with the Lattice QCD results as input, to predict the scattering phase-shift (and threshold parameters) at the phys...

  16. N* Spectroscopy from Lattice QCD: The Roper Explained

    Science.gov (United States)

    Leinweber, Derek; Kamleh, Waseem; Kiratidis, Adrian; Liu, Zhan-Wei; Mahbub, Selim; Roberts, Dale; Stokes, Finn; Thomas, Anthony W.; Wu, Jiajun

    This brief review focuses on the low-lying even- and odd-parity excitations of the nucleon obtained in recent lattice QCD calculations. Commencing with a survey of the 2014-15 literature we'll see that results for the first even-parity excitation energy can differ by as much as 1 GeV, a rather unsatisfactory situation. Following a brief review of the methods used to isolate excitations of the nucleon in lattice QCD, and drawing on recent advances, we'll see how a consensus on the low-lying spectrum has emerged among many different lattice groups. To provide insight into the nature of these states we'll review the wave functions and electromagnetic form factors that are available for a few of these states. Consistent with the Luscher formalism for extracting phase shifts from finite volume spectra, the Hamiltonian approach to effective field theory in finite volume can provide guidance on the manner in which physical quantities manifest themselves in the finite volume of the lattice. With this insight, we will address the question; Have we seen the Roper in lattice QCD?

  17. The K+ K+ scattering length from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Silas Beane; Thomas Luu; Konstantinos Orginos; Assumpta Parreno; Martin Savage; Aaron Torok; Andre Walker-Loud

    2007-09-11

    The K+K+ scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the MILC asqtad-improved gauge configurations with fourth-rooted staggered sea quarks. Three-flavor mixed-action chiral perturbation theory at next-to-leading order, which includes the leading effects of the finite lattice spacing, is used to extrapolate the results of the lattice calculation to the physical value of mK + /fK + . We find mK^+ aK^+ K^+ = â~0.352 ± 0.016, where the statistical and systematic errors have been combined in quadrature.

  18. Extracting Vus from Lattice QCD simulations: Recent progress and prospects

    CERN Document Server

    Garron, Nicolas

    2014-01-01

    I review the current status of the determination of Vus from a lattice perspective. The recent progress are very impressive: computation with 2 + 1 and 2 + 1 + 1 dynamical flavours, physical pion mass, several fine lattices, different discretisation of the QCD Lagrangian, etc. In this report, intended for non-lattice experts, I give an overview of the situation for the computation of fK /f{\\pi} and f+(0), from which Vus and Vud can be extracted. Besides the main features of the new computations, I also present some theoretical ideas developed in the recent years which allow for a cleaner determination of the relevant form factor f+ (0).

  19. Resummation of Cactus Diagrams in Lattice QCD, to all Orders

    CERN Document Server

    Panagopoulos, H

    2000-01-01

    We show how to perform a resummation, to all orders in perturbation theory, of a certain class of gauge invariant tadpole-like diagrams in Lattice QCD. These diagrams are often largely responsible for lattice artifacts. Our resummation leads to an improved perturbative expansion. Applied to a number of cases of interest, e.g. the lattice renormalization of some two-fermion operators, this expansion yields results remarkably close to corresponding nonperturbative estimates. We consider in our study both the Wilson and the clover action for fermions.

  20. Axion cosmology, lattice QCD and the dilute instanton gas

    Energy Technology Data Exchange (ETDEWEB)

    Borsanyi, S. [Wuppertal Univ. (Germany). Dept. of Physics; Dierigl, M.; Ringwald, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Fodor, Z. [Wuppertal Univ. (Germany). Dept. of Physics; Forschungszentrum Juelich (Germany). Inst. for Advanced Simulation (IAS), Juelich Supercomputing Centre (JSC); Lorand Eoetvoes Univ., Budapest (Hungary). Inst. for Theoretical Physics; Katz, S.D. [Lorand Eoetvoes Univ., Budapest (Hungary). Inst. for Theoretical Physics; MTA-ELTE Lenduelet Lattice Gauge Theory Research Group, Budapest (Hungary); Mages, S.W. [Rgensburg Univ. (Germany); Forschungszentrum Juelich (Germany). Inst. for Advanced Simulation (IAS), Juelich Supercomputing Centre (JSC); Nogradi, D. [Lorand Eoetvoes Univ., Budapest (Hungary). Inst. for Theoretical Physics; MTA-ELTE Lenduelet Lattice Gauge Theory Research Group, Budapest (Hungary); Califonia Univ., Santa Barbara, CA (United States). Kavli Inst. for Theoretical Physics; Redondo, J. [Zaragoza Univ. (Spain). Dept. de Fisica Teorica; Max-Planck-Institut fuer Physik, Muenchen (Germany); Szabo, K.K. [Wuppertal Univ. (Germany). Dept. of Physics; Forschungszentrum Juelich (Germany). Inst. for Advanced Simulation (IAS), Juelich Supercomputing Centre (JSC)

    2015-08-15

    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.

  1. 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.)

  2. Baryon number and charge fluctuations from lattice QCD

    CERN Document Server

    Schmidt, Christian

    2012-01-01

    We calculate electric and baryonic charge fluctuations on the lattice. Results have been obtained with the highly improved staggered quark action (HISQ) and almost physical quark masses on lattices with spacial extent of $N_\\tau=6,8,12$. Higher order cumulants of the net-charge distributions are increasingly dominated by a universal scaling behavior, which is arising due to a critical point of QCD in the chiral limit. Considering cumulants up to the sixth order, we observe that they generically behave as expected from universal scaling laws, which is quite different from the cumulants calculated within the hadron resonance gas model. Taking ratios of these cumulants, we obtain volume independent results that can be compared to the experimental measurements. Such a comparison will unambiguously relate the QCD transition temperature that has been determined on the lattice with the freeze out temperature of heavy ion collision at LHC and RHIC.

  3. Axion cosmology, lattice QCD and the dilute instanton gas

    Directory of Open Access Journals (Sweden)

    Sz. Borsanyi

    2016-01-01

    Full Text Available 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.

  4. Lattice QCD as a tool of study for hadron physics

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Atsushi [Hiroshima Univ., Information Media Center, Higashi-Hiroshima, Hiroshima (Japan)

    2002-09-01

    I shall promote Lattice QCD as a tool of study for hadron physics and theoretical nuclear physics. After a brief introduction of the motivation, I will propose several research subjects for the purpose, i.e., 1. opposite parity spectroscopy, 2. hyperon-nucleon and hyperon-hyperon forces by Luescher formula, 3. {sigma} meson, 4. finite temperature: pole and screening masses of hadron, gluon screening mass, QGP transport coefficients, 5. finite density: QCD with SU(2) color, iso-vector chemical potential, response of hadron masses with respect to the chemical potential. (author)

  5. 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.

  6. 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.

  7. Extracting the Omega- electric quadrupole moment from lattice QCD data

    CERN Document Server

    Ramalho, G

    2010-01-01

    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 pr...

  8. 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].

  9. High Statistics Analysis using Anisotropic Clover Lattices: (II) Three-Baryon Systems

    OpenAIRE

    2009-01-01

    We present the results of an exploratory Lattice QCD calculation of three-baryon systems through a high-statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m_\\pi ~ 390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating-operators with the quantum numbers of the $\\Xi^0\\Xi^0 n$ system, one of the least demanding three baryon systems in terms of the number of contracti...

  10. Thermal dilepton rates from quenched lattice QCD

    CERN Document Server

    Ding, H -T; Kaczmarek, O; Karsch, F; Laermann, E; Mukherjee, S; Müller, M; Soeldner, W

    2013-01-01

    We present new lattice results on the continuum extrapolation of the vector current correlation function. Lattice calculations have been carried out in the deconfined phase at a temperature of 1.1 Tc, extending our previous results at 1.45 Tc, utilizing quenched non-perturbatively clover-improved Wilson fermions and light quark masses. A systematic analysis on multiple lattice spacings allows to perform the continuum limit of the correlation function and to extract spectral properties in the continuum limit. Our current analysis suggests the results for the electrical conductivity are proportional to the temperature and the thermal dilepton rates in the quark gluon plasma are comparable for both temperatures. Preliminary results of the continuum extrapolated correlation function at finite momenta, which relates to thermal photon rates, are also presented.

  11. Gluon and Ghost Dynamics from Lattice QCD

    CERN Document Server

    Oliveira, O; Dudal, D; Silva, P J

    2016-01-01

    The two point gluon and ghost correlation functions and the three gluon vertex are investigated, in the Landau gauge, using lattice simulations. For the two point functions, we discuss the approach to the continuum limit looking at the dependence on the lattice spacing and volume. The analytical structure of the propagators is also investigated by computing the corresponding spectral functions using an implementation of the Tikhonov regularisation to solve the integral equation. For the three point function we report results when the momentum of one of the gluon lines is set to zero and discuss its implications.

  12. Gluon and Ghost Dynamics from Lattice QCD

    Science.gov (United States)

    Oliveira, O.; Duarte, A. G.; Dudal, D.; Silva, P. J.

    2017-03-01

    The two point gluon and ghost correlation functions and the three gluon vertex are investigated, in the Landau gauge, using lattice simulations. For the two point functions, we discuss the approach to the continuum limit looking at the dependence on the lattice spacing and volume. The analytical structure of the propagators is also investigated by computing the corresponding spectral functions using an implementation of the Tikhonov regularisation to solve the integral equation. For the three point function we report results when the momentum of one of the gluon lines is set to zero and discuss its implications.

  13. Automated generation of lattice QCD Feynman rules

    Energy Technology Data Exchange (ETDEWEB)

    Hart, A.; Mueller, E.H. [Edinburgh Univ. (United Kingdom). SUPA School of Physics and Astronomy; von Hippel, G.M. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Horgan, R.R. [Cambridge Univ. (United Kingdom). DAMTP, CMS

    2009-04-15

    The derivation of the Feynman rules for lattice perturbation theory from actions and operators is complicated, especially for highly improved actions such as HISQ. This task is, however, both important and particularly suitable for automation. We describe a suite of software to generate and evaluate Feynman rules for a wide range of lattice field theories with gluons and (relativistic and/or heavy) quarks. Our programs are capable of dealing with actions as complicated as (m)NRQCD and HISQ. Automated differentiation methods are used to calculate also the derivatives of Feynman diagrams. (orig.)

  14. Probability distribution functions in the finite density lattice QCD

    CERN Document Server

    Ejiri, S; Aoki, S; Kanaya, K; Saito, H; Hatsuda, T; Ohno, H; Umeda, T

    2012-01-01

    We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. We try to solve the problems which arise in the numerical study of the finite density QCD, focusing on the probability distribution function (histogram). As a first step, we investigate the quark mass dependence and the chemical potential dependence of the probability distribution function as a function of the Polyakov loop when all quark masses are sufficiently large, and study the properties of the distribution function. The effect from the complex phase of the quark determinant is estimated explicitly. The shape of the distribution function changes with the quark mass and the chemical potential. Through the shape of the distribution, the critical surface which separates the first order transition and crossover regions in the heavy quark region is determined for the 2+1-flavor case.

  15. Determining the scale in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Bornyakov, V.G. [Institute for High Energy Physics, Protvino (Russian Federation); Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Far Eastern Federal Univ., Vladivostok (Russian Federation). School of Biomedicine; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Hudspith, R. [York Univ., Toronto, ON (Canada). Dept. of Physics and Astronomy; and others

    2015-12-15

    We discuss scale setting in the context of 2+1 dynamical fermion simulations where we approach the physical point in the quark mass plane keeping the average quark mass constant. We have simulations at four beta values, and after determining the paths and lattice spacings, we give an estimation of the phenomenological values of various Wilson flow scales.

  16. Disconnected Loops with Twisted Mass Lattice QCD

    CERN Document Server

    Wilcox, W; Morgan, R; Lewis, R; Wilcox, Walter; Darnell, Dean; Morgan, Ron; Lewis, Randy

    2005-01-01

    We give a general introduction and discussion of the issues involved in using the twisted mass formulation of lattice fermions in the context of disconnected loop calculations, including a short orientation on the present experimental situation for nucleon strange quark form factors. A prototype calculation of the disconnected part of the nucleon scalar form factor is described.

  17. Determining the scale in Lattice QCD

    CERN Document Server

    Bornyakov, V G; Hudspith, R; Nakamura, Y; Perlt, H; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Stüben, H; Zanotti, J M

    2015-01-01

    We discuss scale setting in the context of 2+1 dynamical fermion simulations where we approach the physical point in the quark mass plane keeping the average quark mass constant. We have simulations at four beta values, and after determining the paths and lattice spacings, we give an estimation of the phenomenological values of various Wilson flow scales.

  18. Transition of $\\rho \\rightarrow \\pi \\gamma$ in Lattice QCD

    CERN Document Server

    Owen, Benjamin J; Leinweber, Derek B; Mahbub, M Selim; Menadue, Benjamin J

    2015-01-01

    With the ongoing experimental interest in exploring the excited hadron spectrum, evaluations of the matrix elements describing the formation and decay of such states via radiative processes provide us with an important connection between theory and experiment. In particular, determinations obtained via the lattice allow for a direct comparison of QCD-expectation with experimental observation. Here we present the first light quark determination of the $\\rho \\rightarrow \\pi \\gamma$ transition form factor from lattice QCD using dynamical quarks. Using the PACS-CS 2+1 flavour QCD ensembles we are able to obtain results across a range of masses, to the near physical value of $m_\\pi = 157$ MeV. An important aspect of our approach is the use of variational methods to isolate the desired QCD eigenstate. For low-lying states, such techniques facilitate the removal of excited state contributions. In principle the method enables one to consider arbitrary eigenstates. We find our results are in accord with the non-relati...

  19. A Framework for Lattice QCD Calculations on GPUs

    CERN Document Server

    Winter, F T; Edwards, R G; Joó, B

    2014-01-01

    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 applica...

  20. B-physics from lattice QCD...with a twist

    CERN Document Server

    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.

  1. Chiral effective theory with a light scalar and lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Soto, J., E-mail: joan.soto@ub.edu [Departament d' Estructura i Constituents de la Materia, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Institut de Ciencies del Cosmos, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Talavera, P., E-mail: pere.talavera@icc.ub.edu [Institut de Ciencies del Cosmos, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Comte Urgell 187, E-08036 Barcelona (Spain); Tarrus, J., E-mail: tarrus@ecm.ub.es [Departament d' Estructura i Constituents de la Materia, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Institut de Ciencies del Cosmos, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

    2013-01-21

    We extend the usual chiral perturbation theory framework ({chi}PT) to allow the inclusion of a light dynamical isosinglet scalar. Using lattice QCD results, and a few phenomenological inputs, we explore the parameter space of the effective theory. We discuss the S-wave pion-pion scattering lengths, extract the average value of the two light quark masses and evaluate the impact of the dynamical singlet field in the low-energy constants l{sup Macron }{sub 1}, l{sup Macron }{sub 3} and l{sup Macron }{sub 4} of {chi}PT. We also show how to extract the mass and width of the sigma resonance from chiral extrapolations of lattice QCD data.

  2. Lattice QCD at finite temperature and density from Taylor expansion

    Science.gov (United States)

    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.

  3. 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

  4. Light hadron spectrum and decay constants in quenched lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Allton, C.R.; Lellouch, L.; Sachrajda, C.T.; Wittig, H. (Physics Department, The University, Southampton SO9 5NH (United Kingdom)); Baxter, R.M.; Booth, S.P.; Bowler, K.C.; Henty, D.S.; Kenway, R.D.; McNeile, C.; Pendleton, B.J.; Richards, D.G.; Simone, J.N.; Simpson, A.D. (Department of Physics, The University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)); (UKQCD Collaboration)

    1994-01-01

    We present results for light hadrons composed of both degenerate and nondegenerate quarks in quenched lattice QCD. We calculate masses and decay constants using 60 gauge configurations with an [ital O]([ital a])-improved fermion action at [beta]=6.2. Using the [rho] mass to set the scale we find hadron masses within two to three standard deviations of the experimental values (given in parentheses): [ital m][sub [ital K

  5. Mass spectrum of 1-+ exotic mesons from lattice QCD

    CERN Document Server

    Cook, M S

    2006-01-01

    Time correlation functions of a hybrid exotic meson operator, with JPC=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 pi1(1400) and pi1(1600), and also to a state in the 2 GeV region carrying the same quantum numbers.

  6. Pion Distribution Amplitude from Lattice QCD

    CERN Document Server

    Braun, V M; Göckeler, M; Pérez-Rubio, P; Schäfer, A; Schiel, R W; Sternbeck, A

    2015-01-01

    We have calculated the second moment of the pion light-cone distribution amplitude using two flavors of dynamical (clover) fermions on lattices of different volumes, lattice spacings between $0.06 \\, \\mathrm {fm}$ and $0.08 \\, \\mathrm {fm}$ and pion masses down to $m_\\pi\\sim 150 \\, \\mathrm {MeV}$. Our result for the second Gegenbauer coefficient is $a_2 = 0.1364(154)(145)$ and for the width parameter $\\langle \\xi^2 \\rangle = 0.2361(41)(39)$. Both numbers refer to the scale $\\mu=2 \\, \\mathrm {GeV}$in the $\\overline{\\text{MS}}$ scheme, the first error is statistical including the uncertainty of the chiral extrapolation, and the second error is the estimated uncertainty coming from the nonperturbatively determined renormalization factors.

  7. Nucleon distribution amplitudes from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Kaltenbrunner, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (DE). John von Neumann-Inst. fuer Computing NIC] (and others)

    2008-04-15

    We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)

  8. Nucleon electromagnetic form factors in twisted mass lattice QCD

    CERN Document Server

    Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, 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. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 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.

  9. 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.)

  10. 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.

  11. Recent progress in hadron structure from Lattice QCD

    CERN Document Server

    Constantinou, Martha

    2015-01-01

    We review recent progress in hadron structure using lattice QCD simulations, with main focus in the evaluation of nucleon quantities such as the axial and tensor charges, and the spin con- tent of the nucleon, using simulations at pion masses close to the physical value. We highlight developments on the evaluation of the gluon moment, a new direct approach to compute quark parton distributions functions on the lattice, as well as, the neutron electric dipole moment. A discussion of the systematic uncertainties and the computation of the disconnected contributions using dynamical simulations is also included.

  12. Long distance part of $\\epsilon_K$ from lattice QCD

    CERN Document Server

    Bai, Ziyuan

    2016-01-01

    We demonstrate the lattice QCD calculation of the long distance contribution to $\\epsilon_K$. Due to the singular, short-distance structure of $\\epsilon_K$, we must perform a short-distance subtraction and introduce a corresponding low-energy constant determined from perturbation theory, which we calculate at Next Leading Order (NLO). We perform the calculation on a $24^3 \\times 64$ lattice with a pion mass of 329 MeV. This work is a complete calculation, which includes all connected and disconnected diagrams.

  13. Moments of nucleon generalized parton distributions from lattice QCD

    CERN Document Server

    Alexandrou, C; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Kallidonis, C; Korzec, T; Papinutto, M

    2011-01-01

    We present results on the lower moments of the nucleon generalized parton distri butions 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 non-perturbatively and the values are given in the $\\bar{\\rm MS}$ scheme at a scale $ \\mu=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.

  14. Moments of nucleon generalized parton distributions from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrou, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Carbonell, J.; Harraud, P.A.; Papinutto, M. [UJF/CNRS/IN2P3, Grenoble (France). Lab. de Physique Subatomique et Cosmologie; Constantinou, M.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Guichon, P. [CEA-Saclay, Gif-sur-Yvette (France). IRFU-Service de Physique Nucleaire; Jansen, K. [DESY, Zeuthen (Germany). NIC; Korzec, T. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Humboldt Univ. Berlin (Germany). Inst. fuer Physik

    2011-07-15

    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 {mu}=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.)

  15. Nucleon resonance structure in the finite volume of lattice QCD

    CERN Document Server

    Wu, Jia-Jun; Lee, T -S H; Leinweber, D B; Thomas, A W

    2016-01-01

    An approach for relating the nucleon resonances extracted from $\\pi N$ reaction data to lattice QCD calculations has been developed by using the finite-volume Hamiltonian method. Within models of $\\pi N$ reactions, bare states are introduced to parametrize the intrinsic excitations of the nucleon. We show that the resonance pole positions can be related to the probability $P_{N^*}(E)$ of finding the bare state, $N^*$, in the $\\pi N$ scattering states in infinite volume. We further demonstrate that the probability $P_{N^*}^V(E)$ of finding the same bare states in the eigenfunctions of the underlying Hamiltonian in finite volume approaches $P_{N^*}(E)$ as the volume increases. Our findings suggest that the comparison of $P_{N^*}(E)$ and $P_{N^*}^V(E)$ can be used to examine whether the nucleon resonances extracted from the $\\pi N$ reaction data within the dynamical models are consistent with lattice QCD calculation. We also discuss the measurement of $P_{N^*}^V(E)$ directly from lattice QCD. The practical diffe...

  16. High-precision scale setting in lattice QCD

    Science.gov (United States)

    Borsányi, Szabolcs; Dürr, Stephan; Fodor, Zoltán; Hoelbling, Christian; Katz, Sándor D.; Krieg, Stefan; Kurth, Thorsten; Lellouch, Laurent; Lippert, Thomas; McNeile, Craig; Szabó, Kálmán K.

    2012-09-01

    Scale setting is of central importance in lattice QCD. It is required to predict dimensional quantities in physical units. Moreover, it determines the relative lattice spacings of computations performed at different values of the bare coupling, and this is needed for extrapolating results into the continuum. Thus, we calculate a new quantity, w 0, for setting the scale in lattice QCD, which is based on the Wilson flow like the scale t 0 (M. Luscher, JHEP 08 (2010) 071). It is cheap and straightforward to implement and compute. In particular, it does not involve the delicate fitting of correlation functions at asymptotic times. It typically can be determined on the few per-mil level. We compute its continuum extrapolated value in 2 + 1-flavor QCD for physical and non-physical pion and kaon masses, to allow for mass-independent scale setting even away from the physical mass point. We demonstrate its robustness by computing it with two very different actions (one of them with staggered, the other with Wilson fermions) and by showing that the results agree for physical quark masses in the continuum limit.

  17. Charmed Tetraquarks Tcc and Tcs from Dynamical Lattice QCD Simulations

    CERN Document Server

    Ikeda, Yoichi; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

    2013-01-01

    Charmed tetraquarks $T_{cc}=(cc\\bar{u}\\bar{d})$ and $T_{cs}=(cs\\bar{u}\\bar{d})$ are studied through the S-wave meson-meson interactions, $D$-$D$, $\\bar{K}$-$D$, $D$-$D^{*}$ and $\\bar{K}$-$D^{*}$, on the basis of the (2+1)-flavor lattice QCD simulations with the pion mass $m_{\\pi} \\simeq $410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson-meson scattering phase shifts are calculated. The phase shifts in the isospin triplet ($I$=1) channels indicate repulsive interactions, while those in the $I=0$ channels suggest attraction, growing as $m_{\\pi}$ decreases. This is particularly prominent in the $T_{cc} (J^P=1^+,I=0)$ channel, though neither bound state nor resonance are found in the range $m_{\\pi} =410-700$ MeV. We make a qualitative comparison of our results with the phenomenological diquark picture.

  18. Charmed tetraquarks Tcc and Tcs from dynamical lattice QCD simulations

    Science.gov (United States)

    Ikeda, Yoichi; Charron, Bruno; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

    2014-02-01

    Charmed tetraquarks Tcc=(ccubardbar) and Tcs=(csubardbar) are studied through the S-wave meson-meson interactions, D-D, Kbar-D, D-D* and Kbar-D*, on the basis of the (2+1)-flavor lattice QCD simulations with the pion mass mπ≃410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson-meson scattering phase shifts are calculated. The phase shifts in the isospin triplet (I=1) channels indicate repulsive interactions, while those in the I=0 channels suggest attraction, growing as mπ decreases. This is particularly prominent in the Tcc (JP=1+,I=0) channel, though neither bound state nor resonance are found in the range mπ=410-700 MeV. We make a qualitative comparison of our results with the phenomenological diquark picture.

  19. Towards Nuclear Reactions from Lattice QCD

    Science.gov (United States)

    Briceno, Raul

    2012-10-01

    In this talk I will motivate the evaluation of nuclear reactions cross sections from Lattice Quantum Chromodynamics (LQCD) and discuss challenges associated with such calculations. In particular, I will explore the connection between the energy spectrum of a three-body system in a finite volume and infinite volume scattering matrix elements using an effective field theoretical approach. The implication of this formalism for studying systems composed of a particle and a bound-state below the bound-state break- up, as well as a trimer state will be discussed. I will show that one in fact recovers a Luscher-like quantization condition for sufficiently low-energy up to exponential corrections in the volume due to the size of the two-particle bound-state. I will briefly discuss the similarities of the three-body problem and that of two- body coupled-channels systems and will comment on challenges in applying the formalism above the inelastic threshold.

  20. Rho resonance parameters from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Dehua; Alexandru, Andrei; Molina, Raquel; Döring, Michael

    2016-08-01

    We perform a high-precision calculation of the phase shifts for $\\pi$-$\\pi$ scattering in the I = 1, J = 1 channel in the elastic region using elongated lattices with two mass-degenerate quark favors ($N_f = 2$). We extract the $\\rho$ resonance parameters using a Breit-Wigner fit at two different quark masses, corresponding to $m_{\\pi} = 226$MeV and $m_{\\pi} = 315$MeV, and perform an extrapolation to the physical point. The extrapolation is based on a unitarized chiral perturbation theory model that describes well the phase-shifts around the resonance for both quark masses. We find that the extrapolated value, $m_{\\rho} = 720(1)(15)$MeV, is significantly lower that the physical rho mass and we argue that this shift could be due to the absence of the strange quark in our calculation.

  1. N* Spectroscopy from Lattice QCD: The Roper Explained

    CERN Document Server

    Leinweber, Derek; Kiratidis, Adrian; Liu, Zhan-Wei; Mahbub, Selim; Roberts, Dale; Stokes, Finn; Thomas, Anthony W; Wu, Jiajun

    2015-01-01

    This brief review focuses on the low-lying even- and odd-parity excitations of the nucleon obtained in recent lattice QCD calculations. Commencing with a survey of the 2014-15 literature we'll see that results for the first even-parity excitation energy can differ by as much as 1 GeV, a rather unsatisfactory situation. Following a brief review of the methods used to isolate excitations of the nucleon in lattice QCD, and drawing on recent advances, we'll see how a consensus on the low-lying spectrum has emerged among many different lattice groups. To provide insight into the nature of these states we'll review the wave functions and electromagnetic form factors that are available for a few of these states. Consistent with the Luscher formalism for extracting phase shifts from finite volume spectra, the Hamiltonian approach to effective field theory in finite volume can provide guidance on the manner in which physical quantities manifest themselves in the finite volume of the lattice. With this insight, we will...

  2. 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.

  3. Numerical techniques for lattice QCD in the {epsilon}-regime

    Energy Technology Data Exchange (ETDEWEB)

    Giusti, L. [European Organization for Nuclear Research, Geneva (Switzerland)]|[CNRS, Luminy, Marseille (France). Centre de Physique Theorique; Hoelbling, C. [CNRS, Luminy, Marseille (France). Centre de Physique Theorique; Luescher, M. [European Organization for Nuclear Research, Geneva (Switzerland); Wittig, H. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2002-12-01

    In lattice QCD it is possible, in principle, to determine the parameters in the effective chiral lagrangian (including weak interaction couplings) by performing numerical simulations in the {epsilon}-regime, i.e. at quark masses where the physical extent of the lattice is much smaller than the Compton wave length of the pion. The use of a formulation of the lattice theory that preserves chiral symmetry is attractive in this context, but the numerical implementation of any such approach requires special care in this kinematical situation due to the presence of some very low eigenvalues of the Dirac operator. We discuss a set of techniques (low-mode preconditioning and adapted-precision algorithms in particular) that make such computations numerically safe and more efficient by a large factor. (orig.)

  4. Numerical techniques for lattice QCD in the $\\epsilon$-regime

    CERN Document Server

    Giusti, Leonardo; Lüscher, Martin; Wittig, H

    2003-01-01

    In lattice QCD it is possible, in principle, to determine the parameters in the effective chiral lagrangian (including weak interaction couplings) by performing numerical simulations in the $\\epsilon$--regime, i.e. at quark masses where the physical extent of the lattice is much smaller than the Compton wave length of the pion. The use of a formulation of the lattice theory that preserves chiral symmetry is attractive in this context, but the numerical implementation of any such approach requires special care in this kinematical situation due to the presence of some very low eigenvalues of the Dirac operator. We discuss a set of techniques (low-mode preconditioning and adapted-precision algorithms in particular) that make such computations numerically safe and more efficient by a large factor.

  5. Determining the QCD coupling from lattice vacuum polarization

    CERN Document Server

    Hudspith, Renwick J; Maltman, Kim; Shintani, Eigo

    2015-01-01

    The QCD coupling appears in the perturbative expansion of the current-current two-point (vacuum polarization) function. Any lattice calculation of vacuum polarization is plagued by several competing non-perturbative effects at small momenta and by discretization errors at large momenta. We work in an intermediate region, computing the vacuum polarization for many off-axis momentum directions on the lattice. Having many momentum directions provides a way to monitor and account for lattice artifacts. Our results are competitive with, and have certain systematic advantages over, the alternate phenomenological determination of the strong coupling from the same light quark vacuum polarization produced by sum rule analyses of hadronic tau decay data.

  6. Determination of $\\varepsilon_K$ using lattice QCD inputs

    CERN Document Server

    Bailey, Jon A; Lee, Weonjong; Park, Sungwoo

    2015-01-01

    We present results for the indirect CP violation parameter $\\varepsilon_K$ determined directly from the standard model using lattice QCD to fix the inputs $\\hat{B}_K$, $\\xi_0$, $|V_{us}|$, and $|V_{cb}|$. We use the FLAG and SWME results for $\\hat{B}_K$. We use the RBC-UKQCD result for $\\xi_0$ determined using the experimental value of $\\varepsilon'/\\varepsilon$ and the lattice result of $\\mathrm{Im}\\,A_2$. To set the Wolfenstein parameter $\\lambda$, we use $|V_{us}|$, which is determined from $K_{\\ell3}$ and $K_{\\mu2}$ decays combined with lattice evaluations of the $K \\to \\pi \\ell \

  7. Strongly interacting particles on an anisotropic kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    Hotta, Chisa; Pollmann, Frank, E-mail: chisa@cc.kyoto-su.ac.j [Kyoto Sangyo University, Department of Physics, Faculty of Science, Kyoto 603-8555, Japan Department of Physics, University of California, Berkeley, CA94720 (United States)

    2009-01-01

    We study a model of strongly interacting spinless fermions and hard-core bosons on an anisotropic kagome lattice near 2/3-filling. Our main focus lies on the strongly anisotropic case in which the nearest-neighbor repulsions V and V' are large compared to the hopping amplitudes |t| and |t'|. When t = t' = 0, the system has a charge ordered insulating ground state where the charges align in striped configurations. Doping one electron or hole into the ground state yields an anisotropic metal at V' > V, where the particle fractionalizes along the V'-bonds while propagates along the V-bonds in a one-body like manner. The sixth order ring exchange processes around the hexagonal unit of the lattice play a crucial role in forming a bound state of fractional charges.

  8. Strongly interacting particles on an anisotropic kagome lattice

    Science.gov (United States)

    Hotta, Chisa; Pollmann, Frank

    2009-01-01

    We study a model of strongly interacting spinless fermions and hard-core bosons on an anisotropic kagome lattice near 2/3-filling. Our main focus lies on the strongly anisotropic case in which the nearest-neighbor repulsions V and V' are large compared to the hopping amplitudes |t| and |t'|. When t = t' = 0, the system has a charge ordered insulating ground state where the charges align in striped configurations. Doping one electron or hole into the ground state yields an anisotropic metal at V' > V, where the particle fractionalizes along the V'-bonds while propagates along the V-bonds in a one-body like manner. The sixth order ring exchange processes around the hexagonal unit of the lattice play a crucial role in forming a bound state of fractional charges.

  9. Highly excited and exotic meson spectrum from dynamical lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek, Robert Edwards, David Richards, Christopher Thomas

    2009-12-01

    Using a new quark-field construction algorithm and a large variational basis of operators, we extract a highly excited isovector meson spectrum on dynamical anisotropic lattices. We show how carefully constructed operators can be used to identify the continuum spin of extracted states. This method allows us to extract, with confidence, excited states, states of high spin and states with exotic quantum numbers, including, for the first time, spin-four states.

  10. Matching the Hagedorn mass spectrum with lattice QCD results

    Science.gov (United States)

    Lo, Pok Man; Marczenko, Michał; Redlich, Krzysztof; Sasaki, Chihiro

    2015-11-01

    Based on recent lattice QCD (LQCD) results obtained at finite temperature, we discuss the modeling of the hadronic phase of QCD in the framework of hadron resonance gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.

  11. Fate of the Tetraquark Candidate Zc(3900) in Lattice QCD

    CERN Document Server

    Ikeda, Yoichi; Doi, Takumi; Gongyo, Shinya; Hatsuda, Tetsuo; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Murano, Keiko; Sasaki, Kenji

    2016-01-01

    The possible exotic meson $Z_{c}(3900)$, found in $e^+ e^-$ reactions, is studied by the method of coupled-channel scattering in lattice QCD. The interaction among $\\pi J/\\psi$, $\\rho \\eta_{c}$ and $\\bar{D}D^{*}$ channels is derived from (2+1)-flavor QCD simulations at $m_{\\pi}=410$-$700$ MeV. The interaction is dominated by the off-diagonal $\\pi J/\\psi$-$\\bar{D}D^{*}$ and $\\rho \\eta_{c}$-$\\bar{D}D^{*}$ couplings, which indicates that the $Z_{c}(3900)$ is not a usual resonance but a threshold cusp. Semi-phenomenological analyses with the coupled-channel interaction are presented to confirm this conclusion.

  12. Topological susceptibility in 2-flavor lattice QCD with fixed topology

    CERN Document Server

    Chiu, T W; Fukaya, H; Hashimoto, S; Hsieh, T H; Kaneko, T; Matsufuru, H; Noaki, J; Ogawa, K; Onogi, T; Yamada, N

    2008-01-01

    We determine the topological susceptibility $ \\chi_t $ in the trivial topological sector generated by lattice simulations of two-flavor QCD with overlap Dirac fermion, on a $16^3 \\times 32$ lattice with lattice spacing $\\sim$ 0.12 fm, at six sea quark masses $m_q$ ranging from $m_s/6$ to $m_s$ (where $m_s$ is the physical strange quark mass). The $ \\chi_t $ is extracted from the plateau (at large time separation) of the time-correlation function of the flavor-singlet pseudoscalar meson ($\\eta'$), which arises from the finite size effect due to fixed topology. In the small $m_q$ regime, our result of $\\chi_t$ is proportional to $m_q$ as expected from chiral effective theory. Using the formula $\\chi_t=m_q\\Sigma/N_f$ by Leutwyler-Smilga, we obtain the chiral condensate in $N_f=2$ QCD as $\\Sigma^{\\bar{\\mathrm{MS}}}(\\mathrm{2 GeV})=[252(5)(10) \\mathrm{MeV}]^3 $, in good agreement with our previous result obtained in the $\\epsilon$-regime.

  13. Interquark potential with finite quark mass from lattice QCD.

    Science.gov (United States)

    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.

  14. 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.

  15. Dyons and Roberge - Weiss transition in lattice QCD

    CERN Document Server

    Bornyakov, V G; Goy, V A; Ilgenfritz, E -M; Martemyanov, B V; Molochkov, A V; Nakamura, Atsushi; Nikolaev, A A; Zakharov, V I

    2016-01-01

    We study lattice QCD with $N_f=2$ Wilson fermions at nonzero imaginary chemical potential and nonzero temperature. We relate the Roberge - Weiss phase transition to the properties of dyons which are constituents of the KvBLL calorons. We present numerical evidence that the characteristic features of the spectral gap of the overlap Dirac operator as function of an angle modifying the boundary condition are determined by the $Z_3$ sector of the respective imaginary chemical potential. We then demonstrate that dyon excitations in thermal configurations could be responsible (in line with perturbative excitations) for these phenomena.

  16. Two Photon Decays of Charmonia from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek; Robert Edwards

    2006-07-12

    We make the first calculation in lattice QCD of two-photon decays of mesons. Working in the charmonium sector, using the LSZ reduction to relate a photon to a sum of hadronic vector eigenstates, we compute form-factors in both the space-like and time-like domains for the transitions {eta}{sub c} {yields} {gamma}*{gamma}* and {chi}{sub c0} {yields} {gamma}*{gamma}*. At the on-shell point we find approximate agreement with experimental world-average values.

  17. Nucleon matrix elements using the variational method in lattice QCD

    CERN Document Server

    Dragos, Jack; Kamleh, Waseem; Leinweber, Derek B; Nakamura, Yoshifumi; Rakow, Paul E L; Schierholz, Gerrit; Young, Ross D; Zanotti, James M

    2016-01-01

    The extraction of hadron matrix elements in lattice QCD using the standard two- and three-point 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 $\\left$ 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.

  18. Recent results for the proton spin decomposition from lattice QCD

    CERN Document Server

    Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Kallidonis, Christos; Koutsou, Giannis; Jansen, Karl; Panagopoulos, Haralambos; Steffens, Fernanda; Vaquero, Alejandro; Wiese, Christian

    2016-01-01

    The exact decomposition of the proton spin has been a much debated topic, on the experimental as well as the theoretical side. In this talk we would like to report on recent non-perturbative results and ongoing efforts to explore the proton spin from lattice QCD. We present results for the relevant generalized form factors from gauge field ensembles that feature a physical value of the pion mass. These generalized form factors can be used to determine the total spin and angular momentum carried by the quarks. In addition we present first results for our ongoing effort to compute the angular momentum of the gluons in the proton.

  19. Exploring quark transverse momentum distributions with lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard U. Musch, Philipp Hagler, John W. Negele, Andreas Schafer

    2011-05-01

    We discuss in detail a method to study transverse momentum dependent parton distribution functions (TMDs) using lattice QCD. To develop the formalism and to obtain first numerical results, we directly implement a bi-local quark-quark operator connected by a straight Wilson line, allowing us to study T-even, "process-independent" TMDs. Beyond results for x-integrated TMDs and quark densities, we present a study of correlations in x and transverse momentum. Our calculations are based on domain wall valence quark propagators by the LHP collaboration calculated on top of gauge configurations provided by MILC with 2+1 flavors of asqtad-improved staggered sea quarks.

  20. Quarkonium-nucleus bound states from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S.  R. [Univ. of Washington, Seattle, WA (United States); Chang, E. [Univ. of Washington, Seattle, WA (United States); Cohen, S.  D. [Univ. of Washington, Seattle, WA (United States); Detmold, W. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Lin, H. -W. [Univ. of Washington, Seattle, WA (United States); Orginos, K. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Parreño, A. [Univ., de Barcelona, Marti Franques (Spain); Savage, M.  J. [Univ. of Washington, Seattle, WA (United States)

    2015-06-11

    Quarkonium-nucleus systems are composed of two interacting hadronic states without common valence quarks, which interact primarily through multi-gluon exchanges, realizing a color van der Waals force. We present lattice QCD calculations of the interactions of strange and charm quarkonia with light nuclei. Both the strangeonium-nucleus and charmonium-nucleus systems are found to be relatively deeply bound when the masses of the three light quarks are set equal to that of the physical strange quark. Extrapolation of these results to the physical light-quark masses suggests that the binding energy of charmonium to nuclear matter is B < 40 MeV.

  1. A precise determination of $\\alpha_{s}$ from lattice QCD

    CERN Document Server

    Davies, C T H; Lepage, G P; Lidsey, A J; Shigemitsu, J; Sloan, J; Davies, C T H; Hornbostel, K; Lepage, G P; Lidsey, A; Shigemitsu, J; Sloan, J

    1994-01-01

    We present a new determination of the QCD strong coupling constant based on precise lattice calculations of the \\Upsilon spectrum. The largest systematic uncertainty in previous such determinations resulted from the absence of vacuum polarization from light quarks. We substantially reduce this error by including two flavors of dynamical light quarks and extrapolating to three. We find \\alphathree_\\V(8.2~\\GeV) = 0.196(3) for three light flavors, corresponding to \\alphafive_\\msbar(M_Z) = 0.115(2). This is significantly more accurate than previous determinations using this or any other technique.

  2. Anisotropic Kondo lattice without Nozieres exhaustion effect

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, M.N. [Physics Department, Arnold Sommerfeld Center for Theoretical Physics and Center for Nano-Science, Ludwig-Maximilians Universitaet Muenchen, 80333 Munich (Germany)]. E-mail: kiselev@physik.uni-wuerzburg.de; Kikoin, K. [Ben-Gurion University of the Negev, Beer-Sheva, 84105 (Israel)]. E-mail: kikoin@bgumail.bgu.ac.il

    2006-05-01

    The properties of layered Anderson/Kondo lattices with metallic electrons confined in 2D xy planes and local spins in insulating layers forming chains in z direction are studied. Each spin possesses its own 2D Kondo cloud, so that the Nozieres' exhaustion problem does not arise. The excitation spectrum is gapless both in charge and spin sectors. Possible experimental realizations of the model are briefly discussed.

  3. On Scale Determination in Lattice QCD with Dynamical Quarks

    CERN Document Server

    De, A K; Maiti, J

    2008-01-01

    Dependence of $a/r_c$ (inverse Sommer parameter in units of lattice spacing $a$) on $am_q$ (quark mass in lattice unit) has been observed in all lattice QCD simulations with sea quarks including the ones with improved actions. How much of this dependence is a scaling violation has remained an intriguing question. Our approach has been to investigate the issue with an action with known lattice artifacts, i.e., the standard Wilson quark and gauge action with $\\beta=5.6$ and 2 degenerate flavors of sea quarks on $ 16^3 \\times 32 $ lattices. In order to study in detail the sea quark mass dependence, measurements are carried out at eight values of the Wilson hopping parameter $\\kappa$ in the range 0.156 - 0.158 corresponding to PCAC quark mass values $am_q$ from about 0.07 to below 0.015. We analyze the static potential by fitting to the familiar phenomenological form and extract $a/r_c$. Though scaling violations may indeed be present for relatively large $am_q$, a consistent scenario at sufficiently small $am_q$...

  4. Applications of lattice QCD techniques for condensed matter systems

    Science.gov (United States)

    Buividovich, P. V.; Ulybyshev, M. V.

    2016-08-01

    We review the application of lattice QCD techniques, most notably the Hybrid Monte Carlo (HMC) simulations, to first-principle study of tight-binding models of crystalline solids with strong inter-electron interactions. After providing a basic introduction into the HMC algorithm as applied to condensed matter systems, we review HMC simulations of graphene, which in the recent years have helped to understand the semimetal behavior of clean suspended graphene at the quantitative level. We also briefly summarize other novel physical results obtained in these simulations. Then we comment on the applicability of hybrid Monte Carlo to topological insulators and Dirac and Weyl semimetals and highlight some of the relevant open physical problems. Finally, we also touch upon the lattice strong-coupling expansion technique as applied to condensed matter systems.

  5. Heavy dense QCD from a 3d effective lattice theory

    CERN Document Server

    Glesaaen, Jonas; Philipsen, Owe

    2015-01-01

    The cold and dense regime of the QCD phase diagram is to this day inaccessible to first principle lattice calculations owing to the sign problem. Here we present progress of an ongoing effort to probe this particularly difficult regime utilising a dimensionally reduced effective lattice theory with a significantly reduced sign problem. The effective theory is derived by combined character and hopping expansion and is valid for heavy quarks near the continuum. We show an extension of the effective theory to order $u^5\\kappa^8$ in the cold regime. A linked cluster expansion is applied to the effective theory resulting in a consistent mechanism for handling the effective theory fully analytically. The new results are consistent with the ones from simulations confirming the viability of analytic methods. Finally we resum the analytical result which doubles the convergence region of the expansion.

  6. Phase transition in finite density and temperature lattice QCD

    CERN Document Server

    Wang, Rui; Gong, Ming; Liu, Chuan; Liu, Yu-Bin; Liu, Zhao-Feng; Ma, Jian-Ping; Meng, Xiang-Fei; Zhang, Jian-Bo

    2015-01-01

    We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of $\\beta$ and $ma$ at the lattice size $24\\times12^{2}\\times6$. The calculation was done in the Taylar expansion formalism. We are able to calculate the first and second order derivatives of $\\langle\\bar{\\psi}\\psi\\rangle$ in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and the magnitude of $\\bar{\\psi}\\psi$ decreases under the influence of finite chemical potential in both channels.

  7. Bootstrap bound for conformal multi-flavor QCD on lattice

    CERN Document Server

    Nakayama, Yu

    2016-01-01

    The recent work by Iha et al shows an upper bound on mass anomalous dimension $\\gamma_m$ of multi-flavor massless QCD at the renormalization group fixed point from the conformal bootstrap in $SU(N_F)_V$ 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 $SU(N_f)_L \\times SU(N_f)_R$ symmetric conformal field theories. For $N_f=8$, our bound implies $\\gamma_m < 1.31$ to avoid dangerously irrelevant operators that are not compatible with the lattice symmetry.

  8. The strangeness contribution to the proton spin 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 compute the strangeness and light-quark contributions {delta}s, {delta}u and {delta}d to the proton spin in n{sub f}=2 lattice QCD at a pion mass of about 285 MeV and at a lattice spacing{approx}0.073 fm, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson action. We carry out the renormalization of these matrix elements which involves mixing between contributions from different quark flavours. Our main result is the small negative value {delta}s{sup MS}({radical}(7.4)GeV) =-0.020(10)(4) of the strangeness contribution to the nucleon spin. (orig.)

  9. Nucleon Helicity and Transversity Parton Distributions from Lattice QCD

    CERN Document Server

    Chen, Jiunn-Wei; Ji, Xiangdong; Lin, Huey-Wen; Zhang, Jian-Hui

    2016-01-01

    We present the first lattice-QCD calculation of the isovector polarized parton distribution functions (both helicity and transversity) using the large-momentum effective field theory (LaMET) approach for direct Bjorken-$x$ dependence. We first review the detailed steps of the procedure in the unpolarized case, then generalize to the helicity and transversity cases. We also derive a new mass-correction formulation for all three cases. We then compare the effects of each finite-momentum correction using lattice data calculated at $M_\\pi\\approx 310$ MeV. Finally, we discuss the implications of these results for the poorly known antiquark structure and predict the sea-flavor asymmetry in the transversely polarized nucleon.

  10. Toward the excited isoscalar meson spectrum from lattice QCD

    Science.gov (United States)

    Dudek, Jozef J.; Edwards, Robert G.; Guo, Peng; Thomas, Christopher E.

    2013-11-01

    We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to ˜400MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between (1)/(2)(uu¯+dd¯) and ss¯ in most JPC channels; one notable exception is the pseudoscalar sector where the approximate SU(3)F octet, singlet structure of the η, η' is reproduced. We extract exotic JPC states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet qq¯ pair, along with nonexotic hybrid mesons embedded in a qq¯-like spectrum.

  11. Toward the excited isoscalar meson spectrum from lattice QCD

    CERN Document Server

    Dudek, Jozef J; Guo, Peng; Thomas, Christopher E

    2013-01-01

    We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to about 400 MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between light and strange in most JPC channels; one notable exception is the pseudoscalar sector where the approximate SU(3)F octet, singlet structure of the {\\eta}, {\\eta}' is reproduced. We extract exotic JPC states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet qqbar pair, along with non-exotic hybrid mesons embedded in a qqbar-like spectrum.

  12. The QCD Abacus A New Formulation for Lattice Gauge Theories

    CERN Document Server

    Brower, R C

    1998-01-01

    A quantum Hamiltonian is constructed for SU(3) lattice QCD entirely from color triplet Fermions --- the standard quarks and a new Fermionic ``constituent'' of the gluon we call ``rishons''. The quarks are represented by Dirac spinors on each site and the gauge fields by rishon-antirishon bilinears on each link which together with the local gauge transforms are the generators of an SU(6) algebra. The effective Lagrangian for the path integral lives in $R^4 \\times S^1$ Euclidean space with a compact ``fifth time'' of circumference ($\\beta$) and non-Abelian charge ($e^2$) both of which carry dimensions of length. For large $\\beta$, it is conjectured that continuum QCD is reached and that the dimensionless ratio $g^2 = e^2/\\beta$ becomes the QCD gauge coupling. The quarks are introduced as Kaplan chiral Fermions at either end of the finite slab in fifth time. This talk will emphasize the gauge and algebraic structure of the rishon or link Fermions and the special properties that may lead to fast discrete dynamics...

  13. The phase diagram of twisted mass lattice QCD

    CERN Document Server

    Sharpe, S R; Sharpe, Stephen R.; Wu, Jackson M. S.

    2004-01-01

    We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m_\\pi^2/(4\\pi f_\\pi)^2 ~ a \\Lambda (a being the lattice spacing, and \\Lambda = \\Lambda_{QCD}). We then focus on the region where m_\\pi^2/(4\\pi f_\\pi)^2 ~ (a \\Lambda)^2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is non-vanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transitio...

  14. 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.)

  15. Sharing lattice QCD data over a widely distributed file system

    Science.gov (United States)

    Amagasa, T.; Aoki, S.; Aoki, Y.; Aoyama, T.; Doi, T.; Fukumura, K.; Ishii, N.; Ishikawa, K.-I.; Jitsumoto, H.; Kamano, H.; Konno, Y.; Matsufuru, H.; Mikami, Y.; Miura, K.; Sato, M.; Takeda, S.; Tatebe, O.; Togawa, H.; Ukawa, A.; Ukita, N.; Watanabe, Y.; Yamazaki, T.; Yoshie, T.

    2015-12-01

    JLDG is a data-grid for the lattice QCD (LQCD) community in Japan. Several large research groups in Japan have been working on lattice QCD simulations using supercomputers distributed over distant sites. The JLDG provides such collaborations with an efficient method of data management and sharing. File servers installed on 9 sites are connected to the NII SINET VPN and are bound into a single file system with the GFarm. The file system looks the same from any sites, so that users can do analyses on a supercomputer on a site, using data generated and stored in the JLDG at a different site. We present a brief description of hardware and software of the JLDG, including a recently developed subsystem for cooperating with the HPCI shared storage, and report performance and statistics of the JLDG. As of April 2015, 15 research groups (61 users) store their daily research data of 4.7PB including replica and 68 million files in total. Number of publications for works which used the JLDG is 98. The large number of publications and recent rapid increase of disk usage convince us that the JLDG has grown up into a useful infrastructure for LQCD community in Japan.

  16. Current status of $\\varepsilon_K$ with lattice QCD inputs

    CERN Document Server

    Bailey, Jon A; Lee, Weonjong; Park, Sungwoo

    2015-01-01

    We present the Standard Model evaluation of the indirect CP violation parameter $\\varepsilon_K$ using inputs determined from lattice QCD together with experiment: $|V_{us}|$, $|V_{cb}|$, $\\xi_0$, and $\\hat{B}_K$. We use the Wolfenstein parametrization ($|V_{cb}|$, $\\lambda$, $\\bar{\\rho}$, $\\bar{\\eta}$) for the CKM matrix elements. For the central value, we take the angle-only fit of the UTfit collaboration, and use $|V_{us}|$ from the $K_{\\ell 3}$ and $K_{\\mu 2}$ decays as an independent input to fix $\\lambda$. For the error estimate, we use results of the global unitarity triangle fits from the CKMfitter and UTfit collaborations. We find that the Standard Model (SM) prediction of $\\varepsilon_K$ with exclusive $V_{cb}$ (lattice QCD results) is lower than the experimental value by $3.6(2)\\sigma$. However, with inclusive $V_{cb}$ (results of heavy quark expansion), the tension between the SM prediction of $\\varepsilon_K$ and its experimental value disappears.

  17. Improvement Of Wilson Fermions And Twisted Mass Lattice Qcd

    CERN Document Server

    Wu, J M

    2005-01-01

    In order for Wilson fermions to be a competitive option to use in lattice QCD (LQCD) simulations, the large inherent discretization errors starting at O(a) (a being the lattice spacing) have to be removed. This can be accomplished through the Symanizk improvement program, where improvement terms have to be added to both the action and the operators of interest with coefficients appropriately chosen so that the rate of convergence to the continuum limit is quadratic in a. For this to be applicable to numerical simulations, improvement coefficients have to be determined non-perturbatively. A program for doing so has been pioneered by the Alpha collaboration. In this work, an extension of that program is made to improve all bilinear operators in QCD with two, three, and four flavours of non-degenerate quarks. With even numbers of quark flavours, an alternative approach is afforded by twisted mass LQCD (tmLQCD), where O(a) improvement in physical quantities can be achieved automatically at maximal twist. In this ...

  18. Lattice QCD at non-vanishing density phase diagram, equation of state

    CERN Document Server

    Csikor, Ferenc; Fodor, Z; Katz, S D; Szabó, K K; Tóth, A I

    2003-01-01

    We propose a method to study lattice QCD at non-vanishing temperature (T) and chemical potential (\\mu). We use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. The critical endpoint (E) of QCD on the Re(\\mu)-T plane is located. We calculate the pressure (p), the energy density (\\epsilon) and the baryon density (n_B) of QCD at non-vanishing T and \\mu.

  19. Glueball Spectrum and Matrix Elements on Anisotropic Lattices

    Energy Technology Data Exchange (ETDEWEB)

    Y. Chen; A. Alexandru; S.J. Dong; T. Draper; I. Horvath; F.X. Lee; K.F. Liu; N. Mathur; C. Morningstar; M. Peardon; S. Tamhankar; B.L. Young; J.B. Zhang

    2006-01-01

    The glueball-to-vacuum matrix elements of local gluonic operators in scalar, tensor, and pseudoscalar channels are investigated numerically on several anisotropic lattices with the spatial lattice spacing ranging from 0.1fm - 0.2fm. These matrix elements are needed to predict the glueball branching ratios in J/{psi} radiative decays which will help identify the glueball states in experiments. Two types of improved local gluonic operators are constructed for a self-consistent check and the finite volume effects are studied. We find that lattice spacing dependence of our results is very weak and the continuum limits are reliably extrapolated, as a result of improvement of the lattice gauge action and local operators. We also give updated glueball masses with various quantum numbers.

  20. Glue spin and helicity in proton from lattice QCD

    CERN Document Server

    Yang, Yi-Bo; Alexandru, Andrei; Draper, Terrence; Glatzmaier, Michael J; Liu, Keh-Fei; Zhao, Yong

    2016-01-01

    We report the first lattice QCD calculation of the glue spin $S_G$ in the nucleon. The lattice calculation is carried out with valence overlap fermions on 2+1 flavor DWF gauge configurations on four lattice spacings and four volumes including an ensemble with physical values for the quark masses. The glue spin $S_G$ in the $\\overline{\\text{MS}}$ scheme is obtained with the 1-loop perturbative matching. We find the results to be fairly insensitive to lattice spacing and quark masses. Since the frame dependence in the kinematic range $0\\leq \\vec{p} \\leq 1.5$ GeV is very mild, we take the first order large momentum expansion correction and determine the glue spin at the large momentum limit to be $S_G$=0.287(55)(16) at the physical pion mass in the $\\overline{\\text{MS}}$ scheme at $\\mu^2=10$ GeV$^2$. If the matching effect between the glue spin and helicity can be neglected, the glue helicity will be the same as the above value.

  1. Kaon matrix elements and CP violation from quenched lattice QCD

    Science.gov (United States)

    Cristian, Calin-Radu

    We report the results of a calculation of the K → pipi matrix elements relevant for the DeltaI = 1/2 rule and epsilon '/epsilon in quenched lattice QCD using domain wall fermions at a fixed lattice spacing of 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 → pi and K → |0> matrix elements of dimension six, four-fermion operators. Through lowest order chiral perturbation theory these yield K → pipi matrix elements, which we then normalize to continuum values through a non-perturbative renormalization technique. For the Delta I = 1/2 rule 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 epsilon '/epsilon; using known central values for standard model parameters, we calculate (-4.0 +/- 2.3) x 10-4 (statistical error only) compared to the current experimental average of (17.2 +/- 1.8) x 10-4. Because we find a large cancellation between the I = 0 and I = 2 contributions to epsilon'/epsilon, 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 have also calculated the kaon B parameter, BK and find BK(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.

  2. Investigation of hadron matter using lattice QCD and implementation of lattice QCD applications on heterogeneous multicore acceleration processors

    Energy Technology Data Exchange (ETDEWEB)

    Winter, Frank

    2011-07-01

    Observables relevant for the understanding of the structure of baryons were determined by means of Monte Carlo simulations of lattice Quantum Chromodynamics (QCD) using 2+1 dynamical quark flavours. Special emphasis was placed on how these observables change when flavour symmetry is broken in comparison to choosing equal masses for the two light and the strange quark. The first two moments of unpolarised, longitudinally, and transversely polarised parton distribution functions were calculated for the nucleon and hyperons. Modern lattice QCD simulations require petaflop computing and beyond, a regime of computing power we just reach today. Heterogeneous multicore computing is getting increasingly important in high performance computing and allows for deploying multiple types of processing elements within a single workflow. In this work new design concepts were developed for an active library (QDP++) exploiting the compute power of a heterogeneous multicore processor (IBM PowerXCell 8i processor). It was possible to run a QDP++ based physics application (Chroma) on an IBM BladeCenter QS22. (orig.)

  3. QCD propagators and vertices from lattice QCD (in memory of Michael Müller-Preußker)

    Science.gov (United States)

    Sternbeck, André

    2017-03-01

    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.

  4. Multiple anisotropic collisions for advection-diffusion Lattice Boltzmann schemes

    Science.gov (United States)

    Ginzburg, Irina

    2013-01-01

    This paper develops a symmetrized framework for the analysis of the anisotropic advection-diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.

  5. The QCD equation of state with charm quarks from lattice QCD

    Science.gov (United States)

    Cheng, Michael

    Recently, there have been several calculations of the QCD equation of state (EoS) on the lattice. These calculations take into account the two light quarks and the strange quark, but have ignored the effects of the charm quark, assuming that the charm mass (mc ≈ 1300 MeV) is exponentially suppressed at the temperatures which are explored. However, future heavy ion collisions, such as those planned at the LHC, may well probe temperature regimes where the charm quarks play an important role in the dynamics of the QGP. We present a calculation of the charm quark contribution to the QCD EoS using p4-improved staggered fermions at Nt = 4, 6, 8. This calculation is done with a quenched charm quark, i.e. the relevant operators are measured using a valence charm quark mass on a 2+1 flavor gauge field background. The charm quark masses are determined by calculating charmonium masses (metac and mJ/Psi) and fixing these mesons to their physical masses. The interaction measure, pressure, energy density, and entropy density are calculated. We find that the charm contribution makes a significant contribution, even down to temperatures as low as the pseudo-critical temperature, Tc. However, there are significant scaling corrections at the lattice spacings that we use, preventing a reliable continuum extrapolation.

  6. 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.)

  7. Cell processor implementation of a MILC lattice QCD application

    CERN Document Server

    Shi, Guochun; Gottlieb, Steven

    2009-01-01

    We present results of the implementation of one MILC lattice QCD application-simulation with dynamical clover fermions using the hybrid-molecular dynamics R algorithm-on the Cell Broadband Engine processor. Fifty-four individual computational kernels responsible for 98.8% of the overall execution time were ported to the Cell's Synergistic Processing Elements (SPEs). The remaining application framework, including MPI-based distributed code execution, was left to the Cell's PowerPC processor. We observe that we only infrequently achieve more than 10 GFLOPS with any of the kernels, which is just over 4% of the Cell's peak performance. At the same time, many of the kernels are sustaining a bandwidth close to 20 GB/s, which is 78% of the Cell's peak. This indicates that the application performance is limited by the bandwidth between the main memory and the SPEs. In spite of this limitation, speedups of 8.7x (for 8x8x16x16 lattice) and 9.6x (for 16x16x16x16 lattice) were achieved when comparing a 3.2 GHz Cell proce...

  8. The infrared behavior of lattice QCD Green's functions. A numerical study of lattice QCD in Landau gauge

    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.)

  9. Aspects of Chiral Symmetry Breaking in Lattice QCD

    Science.gov (United States)

    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

  10. High Statistics Analysis using Anisotropic Clover Lattices: (III) Baryon-Baryon Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Beane, Silas [Univ. of New Hampshire, Durham, NH (United States); Detmold, William [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Lin, Huey-Wen [Univ. of Washington, Seattle, WA (United States); Luu, Thomas C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Orginos, Kostas [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Savage, Martin [Univ. of Washington, Seattle, WA (United States); Torok, Aaron M. [Indiana Univ., Bloomington, IN (United States). Dept. of Physics; Walker-Loud, Andre [College of William and Mary, Williamsburg, VA (United States)

    2010-03-01

    Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m_pi ~ 390 MeV, a spatial volume of L^3 ~ (2.5 fm)^3, and a spatial lattice spacing of b ~ 0.123 fm. Luscher’s method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The N-Sigma interactions are found to be highly spin-dependent, and the interaction in the ^3 S _1 channel is found to be strong. In contrast, the N-Lambda interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is Lambda-Lambda, indicating that the Lambda-Lambda interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of the NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting

  11. High statistics analysis using anisotropic clover lattices: (III) Baryon-baryon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S; Detmold, W; Lin, H; Luu, T; Orginos, K; Savage, M; Torok, A; Walker-Loud, A

    2010-01-19

    Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m{sub {pi}} {approx} 390 MeV, a spatial volume of L{sup 3} {approx} (2.5 fm){sup 3}, and a spatial lattice spacing of b {approx} 0.123 fm. Luescher's method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The isospin-3/2 N{Sigma} interactions are found to be highly spin-dependent, and the interaction in the {sup 3}S{sub 1} channel is found to be strong. In contrast, the N{Lambda} interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is {Lambda}{Lambda}, indicating that the {Lambda}{Lambda} interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting is explored. In particular, focus is placed on the window of time slices for which the signal-to-noise ratio does not degrade exponentially, as this provides the opportunity to extract quantitative information about multi-baryon systems.

  12. Predicting positive parity Bs mesons from lattice QCD

    Directory of Open Access Journals (Sweden)

    C.B. Lang

    2015-11-01

    Full Text Available We determine the spectrum of Bs 1P states using lattice QCD. For the Bs1(5830 and Bs2⁎(5840 mesons, the results are in good agreement with the experimental values. Two further mesons are expected in the quantum channels JP=0+ and 1+ near the BK and B⁎K thresholds. A combination of quark–antiquark and B(⁎ meson–Kaon interpolating fields are used to determine the mass of two QCD bound states below the B(⁎K threshold, with the assumption that mixing with Bs(⁎η and isospin-violating decays to Bs(⁎π are negligible. We predict a JP=0+ bound state Bs0 with mass mBs0=5.711(13(19 GeV. With further assumptions motivated theoretically by the heavy quark limit, a bound state with mBs1=5.750(17(19 GeV is predicted in the JP=1+ channel. The results from our first principles calculation are compared to previous model-based estimates.

  13. 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.

  14. Study of the $Z_c^+$ channel in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Leskovec, Luka [Stefan Inst., Ljubljana; Prelovsek, Sasa [Stefan Inst., Ljubljana; Lang, C. B. [Graz U.; Mohler, Daniel [Fermilab

    2015-04-11

    Several charged charmonium-like hadrons called $Z_c$ have been recently discovered by different experiments. In contrast to conventional hadrons these contain at least two valence quarks and antiquarks ($\\bar{c}c\\bar{d}u$). We perform a lattice QCD simulation of the $I^G(J^{PC})=1^+(1^{+-})$ channel including all relevant two-meson operators under 4.3 GeV: $J/\\psi \\pi$, $\\psi_{2S}\\pi$, $\\psi_{1D}\\pi$, $D \\bar{D}^*$, $D^* \\bar{D}^*$, $\\eta_c \\rho$ as well as additional diquark anti-diquark operators. In our $N_f = 2$ simulation with pion mass at 266 MeV we are able to identify all two-meson levels within the energy region of interest. However we find no additional level identifiable as a candidate for $Z_c$.

  15. Transverse spin structure of the nucleon from lattice QCD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Goeckeler, M.; Schaefer, A. [Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Haegeler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics; Nakamura, Y.; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Division, Dept. of Mathematical Sciences; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Stueben, H. [Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB) (Germany)

    2006-12-15

    We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72 (2005) 094020], we predict that the Boer-Mulders-function h{sub 1} {sup perpendicular} {sup to}, describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. (orig.)

  16. Nucleon matrix elements using the variational method in lattice QCD

    Science.gov (United States)

    Dragos, J.; Horsley, R.; Kamleh, W.; Leinweber, D. B.; Nakamura, Y.; Rakow, P. E. L.; Schierholz, G.; Young, R. D.; Zanotti, J. M.

    2016-10-01

    The extraction of hadron matrix elements in lattice QCD using the standard two- and three-point 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 gA, the scalar current gS, the scalar current gT and the quark momentum fraction ⟨x ⟩ 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.

  17. Lattice QCD Calculations in Nuclear Physics towards the Exascale

    Science.gov (United States)

    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.

  18. On the Statistics of Baryon Correlation Functions in Lattice QCD

    CERN Document Server

    Wagman, Michael L

    2016-01-01

    A systematic analysis of the structure of single-baryon correlation functions calculated with lattice QCD is performed, with a particular focus on characterizing the structure of the noise associated with quantum fluctuations. The signal-to-noise problem in these correlation functions is shown, as long suspected, to result from a sign problem. The log-magnitude and complex phase are found to be approximately described by normal and wrapped normal distributions respectively. Properties of circular statistics are used to understand the emergence of a late time noise region where standard energy measurements are unreliable. Power-law tails in the distribution of baryon correlation functions, associated with stable distributions and "Levy flights", are found to play a central role in their time evolution. A new method of analyzing correlation functions is considered for which the signal-to-noise ratio of energy measurements is constant at late times, rather than degrading exponentially; this permits a reliable ex...

  19. Rare $B$ decays using lattice QCD form factors

    CERN Document Server

    Horgan, R R; Meinel, S; Wingate, M

    2015-01-01

    In this write-up we review and update our recent lattice QCD calculation of $B \\to K^*$, $B_s \\to \\phi$, and $B_s \\to K^*$ form factors [arXiv:1310.3722]. These unquenched calculations, performed in the low-recoil kinematic regime, provide a significant improvement over the use of extrapolated light cone sum rule results. The fits presented here include further kinematic constraints and estimates of additional correlations between the different form factor shape parameters. We use these form factors along with Standard Model determinations of Wilson coefficients to give Standard Model predictions for several observables [arXiv:1310.3887]. The modest improvements to the form factor fits lead to improved determinations of $F_L$, the fraction of longitudinally polarized vector mesons, but have little effect on most other observables.

  20. Spectral Properties of Quarks at Finite Temperature in Lattice QCD

    CERN Document Server

    Kitazawa, Masakiyo

    2009-01-01

    We analyze the quark spectral function above and below the critical temperature for deconfinement and at finite momentum in quenched lattice QCD. It is found that the temporal quark correlation function in the deconfined phase near the critical temperature is well reproduced by a two-pole ansatz for the spectral function. The bare quark mass and momentum dependences of the spectral function are analyzed with this ansatz. In the chiral limit we find that even near the critical temperature the quark spectral function has two collective modes corresponding to the normal and plasmino excitations in the high temperature (T) limit. The pole mass of these modes at zero momentum, which should be identified to be the thermal mass of the quark, is approximately proportional to T in a rather wide range of T in the deconfined phase.

  1. Mott-hadron resonance gas and lattice QCD thermodynamics

    CERN Document Server

    Blaschke, D; Turko, L

    2016-01-01

    We present an effective model for the generic behaviour of hadron masses and phase shifts at finite temperature which shares basic features with recent developments within the PNJL model for correlations in quark matter. On this basis we obtain the transition between a hadron resonance gas phase and the quark gluon plasma in the spirit of the generalized Beth-Uhlenbeck approach where the Mott dissociation of hadrons is encoded in the hadronic phase shifts. We find that the restriction to low-lying hadronic channels is justified by the rather low chiral transition temperature found in recent lattice QCD thermodynamics results. While we work in thermodynamic equilibrium, albeit including the contribution of unstable states, the possible contribution of massive components of the hadron resonance gas may become an aspect of strong nonequilibrium in the evolution of a hadronic fireball.

  2. A local factorization of the fermion determinant in lattice QCD

    CERN Document Server

    Cè, Marco; Schaefer, Stefan

    2016-01-01

    We introduce a factorization of the fermion determinant in lattice QCD with Wilson-type fermions that leads to a bosonic action 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 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.

  3. Baryon properties in meson mediums from lattice QCD

    CERN Document Server

    Nicholson, Amy N

    2013-01-01

    We present results for the ground-state mass shifts of octet baryons due to the presence of a medium of pions or kaons from a lattice QCD calculation performed at a single value of the quark mass, corresponding to a pion mass of $m_\\pi$ ~ 390 MeV, and a spatial volume V ~ (4fm)^3. We use a canonical approach in which correlators are formed using a single baryon propagator and a fixed number of meson propagators, up to n=9. From the ground-state energies we calculate two- and three-body interaction parameters. We also extract combinations of low-energy constants by comparing our results to tree level chiral perturbation theory at non-zero isospin/kaon chemical potential.

  4. Lattice QCD Data and Metadata Archives at Fermilab and the International Lattice Data Grid

    CERN Document Server

    Neilsen, E H; Simone, James

    2005-01-01

    The lattice gauge theory community produces large volumes of data. Because the data produced by completed computations form the basis for future work, the maintenance of archives of existing data and metadata describing the provenance, generation parameters, and derived characteristics of that data is essential not only as a reference, but also as a basis for future work. Development of these archives according to uniform standards both in the data and metadata formats provided and in the software interfaces to the component services could greatly simplify collaborations between institutions and enable the dissemination of meaningful results. This paper describes the progress made in the development of a set of such archives at the Fermilab lattice QCD facility. We are coordinating the development of the interfaces to these facilities and the formats of the data and metadata they provide with the efforts of the international lattice data grid (ILDG) metadata and middleware working groups, whose goals are to d...

  5. Thermodynamics of strong interaction matter from lattice QCD and the hadron resonance gas model

    CERN Document Server

    Karsch, Frithjof

    2013-01-01

    We compare recent lattice QCD calculations of higher order cumulants of net-strangeness fluctuations with hadron resonance gas (HRG) model calculations. Up to the QCD transition temperature Tc=( 154 +/- 9) MeV we find good agreement between QCD and HRG model calculations of second and fourth order cumulants, even when subtle aspects of net-baryon number, strangeness and electric charge fluctuations are probed. In particular, the fourth order cumulants indicate that also in the strangeness sector of QCD the failure of HRG model calculations sets in quite abruptly in the vicinity of the QCD transition temperature and is apparent in most observables for T > 160 MeV.

  6. Hamiltonian Effective Field Theory Study of the N^{*}(1535) Resonance in Lattice QCD.

    Science.gov (United States)

    Liu, Zhan-Wei; Kamleh, Waseem; Leinweber, Derek B; Stokes, Finn M; Thomas, Anthony W; Wu, Jia-Jun

    2016-02-26

    Drawing on experimental data for baryon resonances, Hamiltonian effective field theory (HEFT) is used to predict the positions of the finite-volume energy levels to be observed in lattice QCD simulations of the lowest-lying J^{P}=1/2^{-} nucleon excitation. In the initial analysis, the phenomenological parameters of the Hamiltonian model are constrained by experiment and the finite-volume eigenstate energies are a prediction of the model. The agreement between HEFT predictions and lattice QCD results obtained on volumes with spatial lengths of 2 and 3 fm is excellent. These lattice results also admit a more conventional analysis where the low-energy coefficients are constrained by lattice QCD results, enabling a determination of resonance properties from lattice QCD itself. Finally, the role and importance of various components of the Hamiltonian model are examined.

  7. 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.

  8. eta and eta ' mesons from N-f=2+1+1 twisted mass lattice QCD

    NARCIS (Netherlands)

    Ottnad, Konstantin; Michael, Chris; Reker, Siebren; Urbach, Carsten

    2012-01-01

    We determine mass and mixing angles of eta and eta' states using N-f = 2 + 1 + 1 Wilson twisted mass lattice QCD. We describe how those flavour singlet states need to be treated in this lattice formulation. Results are presented for three values of the lattice spacing, a = 0.061 fm, a = 0.078 fm and

  9. Properties of B-mesons in lattice QCD

    CERN Document Server

    Duncan, A; Flynn, J; Hill, B; Hockney, G M; Thacker, H B

    1995-01-01

    The results of an extensive study of B-meson properties in quenched lattice QCD are presented. The studies are carried out in the static quark limit where the b-quark is taken to be infinitely massive. Our computations rely on a multistate smearing method introduced previously, with smearing functions generated from a relativistic lattice quark model. Systematic errors arising from excited state contamination, finite volume effects, and the chiral extrapolation for the light quarks are estimated. We obtain continuum results for the mass splitting M_{B_s}- M_{B_u} = 86 (+/-)12(stat) {+7/-9}(syst) MeV, the ratio of decay constants f_{B_s}/f_{B_u} = 1.22 (+/-)0.04(stat) (+/-)0.02 (syst). For the B-meson decay constant we separately exhibit the sizable uncertainties in the extrapolation to the continuum limit a -> 0 and higher order perturbative matching. We obtain f_{B} = 188 (+/-)23(stat) (+/-)15(syst) {+26/-0}(extrap) (+/-)14 (pert) MeV.

  10. Sivers and Boer-Mulders observables from lattice QCD.

    Energy Technology Data Exchange (ETDEWEB)

    B.U. Musch, Ph. Hagler, M. Engelhardt, J.W. Negele, A. Schafer

    2012-05-01

    We present a first calculation of transverse momentum dependent nucleon observables in dynamical lattice QCD employing non-local operators with staple-shaped, 'process-dependent' Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and in particular to access non-universal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm gear function g{sub 1}T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an n{sub f} = 2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.

  11. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD.

    Science.gov (United States)

    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.

  12. Chiral effective theory with a light scalar and lattice QCD

    CERN Document Server

    Soto, J; Tarrús, J

    2011-01-01

    We extend the usual chiral perturbation theory framework ($\\chi$PT) to allow the inclusion of a light dynamical isosinglet scalar. Using lattice QCD results, and a few phenomenological inputs, we explore the parameter space of the effective theory. The extended theory collects already at LO the ball park contribution to the pion mass and decay constant, thus achieving an accuracy that is comparable to the one of the standard $\\chi$PT at NLO results. We check explicitly that radiative corrections do not spoil this behavior and keep the theory stable under mild variations of the parameters. The parameter sets that are compatible with the current mass and width of the sigma resonance turn out to reproduce the experimental values of the S-wave pion-pion scattering lengths very accurately. We also extract the average value of the two light quark--masses and evaluate the impact of the dynamical singlet field in the low--energy constants $\\bar{l}_3$ and $\\bar{l}_4$ of $\\chi$PT. We emphasize that more accurate lattic...

  13. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD

    CERN Document Server

    Bhattacharya, Tanmoy; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram

    2015-01-01

    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 $\\overline{\\text{MS}}$ 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 (BSM). 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 $d_n < 4 \\times 10^{-28} \\, e$ cm for the neutron EDM in this scenario.

  14. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD

    Science.gov (United States)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram; Pndme Collaboration

    2015-11-01

    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 gTd -u=1.020 (76 ), gTd=0.774 (66 ), gTu=-0.233 (28 ), and gTs=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 C P 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 dnEDM in this scenario.

  15. 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).

  16. 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).

  17. 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.)

  18. Future applications of the Yang-Mills gradient flow in lattice QCD

    CERN Document Server

    Lüscher, Martin

    2013-01-01

    The Yang--Mills gradient flow has many interesting applications in lattice QCD. In this talk, some recent and possible future uses of the flow are discussed, emphasizing the underlying theoretical concepts rather than any computational aspects.

  19. J.J. Sakurai Prize for Theoretical Particle Physics: 40 Years of Lattice QCD

    Science.gov (United States)

    Lepage, Peter

    2016-03-01

    Lattice QCD was invented in 1973-74 by Ken Wilson, who passed away in 2013. This talk will describe the evolution of lattice QCD through the past 40 years with particular emphasis on its first years, and on the past decade, when lattice QCD simulations finally came of age. Thanks to theoretical breakthroughs in the late 1990s and early 2000s, lattice QCD simulations now produce the most accurate theoretical calculations in the history of strong-interaction physics. They play an essential role in high-precision experimental studies of physics within and beyond the Standard Model of Particle Physics. The talk will include a non-technical review of the conceptual ideas behind this revolutionary development in (highly) nonlinear quantum physics, together with a survey of its current impact on theoretical and experimental particle physics, and prospects for the future. Work supported by the National Science Foundation.

  20. On calculating disconnected-type hadronic light-by-light scattering diagrams from lattice QCD

    CERN Document Server

    Hayakawa, M; Christ, N H; Izubuchi, T; Jin, L C; Lehner, C

    2015-01-01

    For reliable comparison of the standard model prediction to the muon g-2 with its experimental value, the hadronic light-by-light scattering (HLbL) contribution must be calculated by lattice QCD simulation. HLbL contribution has many types of disconnected-type diagrams. Here, we start with recalling the point that must be taken care of in every method to calculate them by lattice QCD, and present one concrete method called nonperturbative QED method.

  1. A new method to study lattice QCD at finite temperature and chemical potential

    CERN Document Server

    Fodor, Z

    2002-01-01

    Due to the sign problem, it is exponentially difficult to study QCD on the lattice at finite chemical potential. In this letter we propose a method --an overlap ensuring multi-parameter reweighting technique-- to solve the problem. We apply this method and give the phase diagram of four-flavor QCD obtained on lattices 4^4 and 4\\cdot6^3. Our results are based on {\\cal{O}}(10^3-10^4) configurations.

  2. QCD at nonzero chemical potential: Recent progress on the lattice

    Energy Technology Data Exchange (ETDEWEB)

    Aarts, Gert; Jäger, Benjamin [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); Attanasio, Felipe [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); CAPES Foundation, Ministry of Education of Brazil, Brasília - DF 70040-020 (Brazil); Seiler, Erhard [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), 80805 München (Germany); Sexty, Dénes [Department of Physics, University of Wuppertal, 42119 Wuppertal (Germany); Stamatescu, Ion-Olimpiu [Institut für Theoretische Physik, Universität Heidelberg, 69120 Heidelberg (Germany)

    2016-01-22

    We summarise recent progress in simulating QCD at nonzero baryon density using complex Langevin dynamics. After a brief outline of the main idea, we discuss gauge cooling as a means to control the evolution. Subsequently we present a status report for heavy dense QCD and its phase structure, full QCD with staggered quarks, and full QCD with Wilson quarks, both directly and using the hopping parameter expansion to all orders.

  3. Conformal Window and Correlation Functions in Lattice Conformal QCD

    Science.gov (United States)

    Iwasaki, Y.

    We discuss various aspects of Conformal Field Theories on the Lattice. We mainly investigate the SU(3) gauge theory with Nf degenerate fermions in the fundamental representation, employing the one-plaquette gauge action and the Wilson fermion action. First we make a brief review of our previous works on the phase structure of lattice gauge theories in terms of the gauge coupling constant and the quark mass. We thereby clarify the reason why we conjecture that the conformal window is 7 ≤ Nf ≤ 16. Secondly, we introduce a new concept, "conformal theories with IR cutof" and point out that any numerical simulation on a lattice is bounded by an IR cutoff ∧IR. Then we make predictions that when Nf is within the conformal window, the propagator of a meson G(t) behaves at large t, as G(t) = c exp (-mHt)/tα, that is, a modified Yukawa-type decay form, instead of the usual exponential decay form exp (-mHt), in the small quark mass region. This holds on an any lattice for any coupling constant g, as far as g is between 0 and g*, where g* is the IR fixed point. We verify that numerical results really satisfy the predictions for the Nf = 7 case and the Nf = 16 case. Thirdly, we discuss small number of flavors (Nf = 2 ˜ 6) QCD at finite temperatures. We point out theoretically and verify numerically that the correlation functions at T/Tc > 1 exhibit the characteristics of the conformal function with IR cutoff, an exponential decay with power correction. Investigating our numerical data by a new method which we call the "local-analysis" of propagators, we observe that the Nf = 7 case and the Nf = 2 at T ˜ 2Tc case are similar to each other, while the Nf = 16 case and the Nf = 2 at T = 102 ˜ 105Tc cases are similar to each other. Further, we observe our data are consistent with the picture that the Nf = 7 case and the Nf = 2 at T ˜ 2Tc case are close to the meson unparticle model. On the other hand, the Nf = 16 case and the Nf = 2 at T = 102 ˜ 105Tc cases are close to

  4. Evidence for a Bound H Dibaryon from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S. R. [Albert Einstein fur Fundamentale Physik, Bern (Switzerland); Univ. of New Hampshire, Durham, NH (United States); Chang, E. [Univ. of Barcelona (Spain); Detmold, W. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Joo, B. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Lin, H. W. [Univ. of Washington, Seattle, WA (United States); Luu, T. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Orginos, K. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Parreño, A. [Univ. of Barcelona (Spain); Savage, M. J. [Univ. of Washington, Seattle, WA (United States); Torok, A. [Indiana Univ., Bloomington, IN (United States); Walker-Loud, A.

    2011-04-20

    We present evidence for the existence of a bound H-dibaryon, an I = 0, J = 0, s = -2 state with valence quark structure uuddss, at a pion mass of m$_{\\pi}$ ~389 MeV. Extrapolating the results of lattice QCD calculations performed on four ensembles of anisotropic clover gauge-field configurations, with spatial extents of L ~ 2.0, 2.5, 3.0 and 3.9 fm at a spatial lattice spacing of bs ~ 0.123 fm, we find an H-dibaryon bound by B$H\\atop{\\infty}$ = 16.6 ± 2.1 ± 4.6 MeV at a pion mass of m$_{\\pi}$ ~ 389 MeV.

  5. Lattice determination of the critical point of QCD at finite $T$ and $\\mu$

    CERN Document Server

    Fodor, Z

    2002-01-01

    Based on universal arguments it is believed that there is a critical point (E) in QCD on the temperature (T) versus chemical potential (\\mu) plane, which is of extreme importance for heavy-ion experiments. Using finite size scaling and a recently proposed lattice method to study QCD at finite \\mu we determine the location of E in QCD with n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. Our result is T_E=160 \\pm 3.5 MeV and

  6. Full determination of the CKM matrix using recent results from lattice QCD

    CERN Document Server

    Okamoto, M

    2005-01-01

    A full determination of the CKM matrix using recent results from lattice QCD is presented. To extract the CKM matrix in a uniform fashion, I exclusively use results from unquenched lattice QCD as the theory input for nonperturbative QCD effects. All 9 CKM matrix elements and all 4 Wolfenstein parameters are obtained from results for gold-plated quantities, which include semileptonic decay form factors and leptonic decay constants of B, D and K mesons, and B^0-\\bar{B}^0 and K^0-\\bar{K}^0 mixing amplitudes.

  7. Lattice QCD with chemical potential: Evading the fermion-sign problem

    Indian Academy of Sciences (India)

    Sourendu Gupta

    2004-12-01

    Since the turn of the millennium there has been tremendous progress in understanding QCD at finite chemical potential, . Apart from qualitative results obtained using models, and exact results at very large obtained in weak coupling theory, there has been tremendous progress in getting exact and quantitative results from lattice simulations. I summarize the status of lattice QCD at finite chemical potential – locating the critical end-point in the QCD phase diagram, predicting event-to-event fluctuation rates of conserved quantities, and finding the rate of strangeness production.

  8. The Magnetic Structure of Light Nuclei from Lattice QCD

    CERN Document Server

    Chang, Emmanuel; Orginos, Kostas; Parreno, Assumpta; Savage, Martin J; Tiburzi, Brian C; Beane, Silas R

    2015-01-01

    Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei with $A\\le4$, along with the cross-section for the $M1$ transition $np\\rightarrow d\\gamma$, at the flavor SU(3)-symmetric point where the pion mass is $m_\\pi\\sim 806$ MeV. These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent Letter. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter non-trivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with $\\beta_p=5.22(+0.66/-0.45)(0.23) \\times 10^{-4}$ fm$^3$ and $\\beta_n=1.253(+0.056/-0.067)(0.055) \\times 10^{-4}$ fm$^3$, exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses and its magnetic polarizability, $\\beta...

  9. High Statistics Analysis using Anisotropic Clover Lattices: (IV) The Volume Dependence of the Light Hadron Masses

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S R; Detmold, W; Lin, H W; Luu, T C; Orginos, K; Parreno, A; Savage, M J; Torok, A; Walker-Loud, A

    2011-07-01

    The volume dependence of the octet baryon masses and relations among them are explored with Lattice QCD. Calculations are performed with nf = 2 + 1 clover fermion discretization in four lattice volumes, with spatial extent L ? 2.0, 2.5, 3.0 and 4.0 fm, with an anisotropic lattice spacing of b_s ? 0.123 fm in the spatial direction, and b_t = b_s/3.5 in the time direction, and at a pion mass of m_\\pi ? 390 MeV. The typical precision of the ground-state baryon mass determination is lattice gauge-field configurations. Finally, the volume dependence of the pion and kaon masses are analyzed with two-flavor and three-flavor chiral perturbation theory.

  10. Bilinear-biquadratic anisotropic Heisenberg model on a triangular lattice

    Energy Technology Data Exchange (ETDEWEB)

    Pires, A.S.T., E-mail: antpires@fisica.ufmg.br

    2013-08-15

    Motivated by the fact that the study of disordered phases at zero temperature is of great interest, I study the spin-one quantum antiferromagnet with a next-nearest neighbor interaction on a triangular lattice with bilinear and biquadratic exchange interactions and a single ion anisotropy, using a SU(3) Schwinger boson mean-field theory. I calculate the critical properties, at zero temperature, for values of the single ion anisotropy parameter D above a critical value D{sub C}, where a quantum phase transition takes place from a higher D disordered phase to a lower D ordered phase. - Highlights: • The quantum phase transition of the bilinear-biquadratic anisotropic antiferromagnet is studied. • The effect of competing interaction is analyzed. • The zero temperature phase diagram is obtained.

  11. Resummation of Cactus Diagrams in the Clover Improved Lattice Formulation of QCD

    CERN Document Server

    Panagopoulos, H

    1999-01-01

    We extend to the clover improved lattice formulation of QCD the resummation of cactus diagrams, i.e. a certain class of tadpole-like gauge invariant diagrams. Cactus resummation yields an improved perturbative expansion. We apply it to the lattice renormalization of some two-fermion operators improving their one-loop perturbative estimates.

  12. Lattice QCD study of a five-quark hadronic molecule

    CERN Document Server

    Cook, M S

    2007-01-01

    We compute the ground-state energies of a heavy-light K-Lambda like system as a function of the relative distance r of the hadrons. The heavy quarks, one in each hadron, are treated as static. Then, the energies give rise to an adiabatic potential Va(r) which we use to study the structure of the five-quark system. The simulation is based on an anisotropic and asymmetric lattice with Wilson fermions. Energies are extracted from spectral density functions obtained with the maximum entropy method. Our results are meant to give qualitative insight: Using the resulting adiabatic potential in a Schroedinger equation produces bound state wave functions which indicate that the ground state of the five-quark system resembles a hadronic molecule, whereas the first excited state, having a very small rms radius, is probably better described as a five-quark cluster, or a pentaquark. We hypothesize that an all light-quark pentaquark may not exist, but in the heavy-quark sector it might, albeit only as an excited state.

  13. Pion Structure in Qcd: from Theory to Lattice to Experimental Data

    Science.gov (United States)

    Bakulev, A. P.; Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.

    We describe the present status of the pion distribution amplitude (DA) as it originates from several sources: (i) a nonperturbative approach based on QCD sum rules with nonlocal condensates, (ii) an O(as) QCD analysis of the CLEO data on Fgg*p(Q2) with asymptotic and renormalon models for higher twists and (iii) recent high-precision lattice QCD calculations of the second moment of the pion DA. We show predictions for the pion electromagnetic form factor, obtained in analytic QCD perturbation theory, and compare it with the JLab data on Fp(Q2). We also discuss in this context an improved model for nonlocal condensates in QCD and show its consequences for the pion DA and the gg*p transition form factor. We include a brief analysis of meson-induced massive lepton (muon) Drell-Yan production for the process p-Nm+m-X, considering both an unpolarized nucleon target and longitudinally polarized protons.

  14. On the Determination of Elastic and Inelastic Nuclear Observables from Lattice QCD

    OpenAIRE

    Briceno, Raul A.

    2013-01-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of the strong interaction, Quantum Chromodynamics (QCD). Currently, lattice QCD (LQCD) provides the only reliable option for performing calculations of low-energy hadronic observables. LQCD calculations are necessarily performed in a finite Euclidean spacetime. As a result, it is necessary to construct formalism that maps the finite-volume observables de...

  15. Excited states in lattice QCD with the stochastic LapH method

    CERN Document Server

    Bulava, John; Foley, Justin; Jhang, You-Cyuan; Juge, Keisuke J; Lenkner, David; Morningstar, Colin; Wong, Chik Him

    2014-01-01

    Progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Results in the zero-momentum bosonic I=1/2, S=1, T1u symmetry sector of QCD using a correlation matrix of 58 operators are presented. All needed Wick contractions are efficiently evaluated using a stochastic method of treating the low-lying modes of quark propagation that exploits Laplacian Heaviside quark-field smearing. Level identification using probe operators is discussed.

  16. Recent lattice results on finite temperature and density QCD, part I

    CERN Document Server

    Karsch, Frithjof

    2007-01-01

    We discuss recent progress made studies of bulk thermodynamics of strongly interacting matter through lattice simulations of QCD with an almost physical light and strange quark mass spectrum. We present results on the QCD equation of state at vanishing and non-vanishing quark chemical potential and show first results on baryon number and strangeness fluctuations, which might be measured in event-by-event fluctuations in low energy runs at RHIC as well as at FAIR.

  17. QCD at non-zero temperature and density from the lattice

    CERN Document Server

    Allton, C R; Hands, S J; Kaczmarek, O; Karsch, Frithjof; Laermann, E; Schmidt, C; Schmidt, Ch.

    2005-01-01

    The study of systems as diverse as the cores of neutron stars and heavy-ion collision experiments requires the understanding of the phase structure of QCD at non-zero temperature, T, and chemical potential, mu_q. We review some of the difficulties of performing lattice simulations of QCD with non-zero mu_q, and outline the re-weighting method used to overcome this problem. This method is used to determine the critical endpoint of QCD in the (mu_q,T) plane. We study the pressure and quark number susceptibility at small mu_q.

  18. Isospin splittings of meson and baryon masses from three-flavor lattice QCD + QED

    CERN Document Server

    Horsley, R; Perlt, H; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Stokes, R; Stüben, H; Young, R D; Zanotti, J M

    2015-01-01

    Lattice QCD simulations are now reaching a precision where isospin breaking effects become important. Previously, we have developed a program to systematically investigate the pattern of flavor symmetry beaking within QCD and successfully applied it to meson and baryon masses involving up, down and strange quarks. In this Letter we extend the calculations to QCD + QED and present our first results on isospin splittings in the pseudoscalar meson and baryon octets. In particular, we obtain $M_{\\pi^+}-M_{\\pi^0}=4.60(20)\\,\\mbox{MeV}$ and $M_n-M_p=1.35(18)\\,\\mbox{MeV}$.

  19. Another mean field treatment in the strong coupling limit of lattice QCD

    OpenAIRE

    Ohnishi, Akira; Miura, Kohtaroh; Nakano, Takashi Z.

    2011-01-01

    We discuss the QCD phase diagram in the strong coupling limit of lattice QCD by using a new type of mean field coming from the next-to-leading order of the large dimensional expansion. The QCD phase diagram in the strong coupling limit recently obtained by using the monomer-dimer-polymer (MDP) algorithm has some differences in the phase boundary shape from that in the mean field results. As one of the origin to explain the difference, we consider another type of auxiliary field, which corresp...

  20. Spontaneous chiral-symmetry breaking of lattice QCD with massless dynamical quarks

    Institute of Scientific and Technical Information of China (English)

    LUO XiangQian

    2007-01-01

    One of the most challenging issues in QCD is the investigation of spontaneous chiral-symmetry breaking,which is characterized by the non-vanishing chiral condensate when the bare fermion mass is zero.In standard methods of the lattice gauge theory,one has to perform expensive simulations at multiple bare quark masses,and employ some modeled functions to extrapolate the data to the chiral limit.This paper applies the probability distribution function method to computing the chiral condensate in lattice QCD with massless dynamical quarks,without any ambiguous mass extrapolation.The results for staggered quarks indicate that this might be a promising and efficient method for investigating the spontaneous chiral-symmetry breaking in lattice QCD,which deserves further investigation.

  1. Spontaneous chiral-symmetry breaking of lattice QCD with massless dynamical quarks

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    One of the most challenging issues in QCD is the investigation of spontaneous chiral-symmetry breaking, which is characterized by the non-vanishing chiral condensate when the bare fermion mass is zero. In standard methods of the lattice gauge theory, one has to perform expensive simulations at multiple bare quark masses, and employ some modeled functions to extrapolate the data to the chiral limit. This paper applies the probability distribution function method to computing the chiral condensate in lattice QCD with massless dynamical quarks, without any ambiguous mass extrapolation. The results for staggered quarks indicate that this might be a promising and efficient method for investigating the spontaneous chiral-symmetry breaking in lattice QCD, which deserves further investigation.

  2. High Statistics Analysis using Anisotropic Clover Lattices: (II) Three-Baryon Systems

    Energy Technology Data Exchange (ETDEWEB)

    Andre Walker-Loud, Will Detmold, William Detmold, Aaron Torok, Konstantinos Orginos, Silas Beane, Tom Luu, Martin Savage, Assumpta Parreno

    2009-10-01

    We present the results of an exploratory Lattice QCD calculation of three-baryon systems through a high-statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m_\\pi ~ 390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating-operators with the quantum numbers of the $\\Xi^0\\Xi^0 n$ system, one of the least demanding three baryon systems in terms of the number of contractions. We find that the ground state of this system has an energy of E_{\\Xi^0\\Xi^0n}= 3877.9\\pm 6.9\\pm 9.2\\pm3.3 MeV corresponding to an energy-shift due to interactions of \\delta E_{\\Xi^0\\Xi^0n}=E_{\\Xi^0\\Xi^0n}-2M_{\\Xi^0} -M_n=4.6\\pm 5.0\\pm 7.9\\pm 4.2 MeV. There are a significant number of time-slices in the three-baryon correlation function for which the signal-to-noise ratio is only slowly degrading with time. This is in contrast to the exponential degradation of the signal-to-noise ratio that is observed at larger times, and is due to the suppressed overlap of the source and sink interpolating-operators that are associated with the variance of the three-baryon correlation function onto the lightest eigenstates in the lattice volume (mesonic systems). As one of the motivations for this area of exploration is the calculation of the structure and reactions of light nuclei, we also present initial results for a system with the quantum numbers of the triton (pnn). This present work establishes a path to multi-baryon systems, and shows that Lattice QCD calculations of the properties and interactions of systems containing four and five baryons are now within sight.

  3. High Statistics Analysis using Anisotropic Clover Lattices: (II) Three-Baryon Systems

    Energy Technology Data Exchange (ETDEWEB)

    Beane, S; Detmold, W; Luu, T; Orginos, K; Parreno, A; Savage, M; Torok, A; Walker-Loud, A

    2009-05-05

    We present the results of an exploratory Lattice QCD calculation of three-baryon systems through a high-statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m{sub {pi}} {approx} 390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating-operators with the quantum numbers of the {Xi}{sup 0}{Xi}{sup 0}n system, one of the least demanding three baryon systems in terms of the number of contractions. We find that the ground state of this system has an energy of E{sub {Xi}{sup 0}{Xi}{sup 0}n} = 3877.9 {+-} 6.9 {+-} 9.2 {+-} 3.3 MeV corresponding to an energy-shift due to interactions of {delta}E{sub {Xi}{sup 0}{Xi}{sup 0}n} = E{sub {Xi}{sup 0}{Xi}{sup 0}n} - 2M{sub {Xi}{sup 0}} - M{sub n} = 4.6 {+-} 5.0 {+-} 7.9 {+-} 4.2 MeV. There are a significant number of time-slices in the three-baryon correlation function for which the signal-to-noise ratio is only slowly degrading with time. This is in contrast to the exponential degradation of the signal-to-noise ratio that is observed at larger times, and is due to the suppressed overlap of the source and sink interpolating-operators that are associated with the variance of the three-baryon correlation function onto the lightest eigenstates in the lattice volume (mesonic systems). As one of the motivations for this area of exploration is the calculation of the structure and reactions of light nuclei, we also present initial results for a system with the quantum numbers of the triton (pnn). This present work establishes a path to multi-baryon systems, and shows that Lattice QCD calculations of the properties and interactions of systems containing four and five baryons are now within sight.

  4. Lattice QCD in the {epsilon}-regime and random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Giusti, L.; Luescher, M. [CERN, Geneva (Switzerland); Weisz, P. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Wittig, H. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2003-11-01

    In the {epsilon}-regime of QCD the main features of the spectrum of the low-lying eigenvalues of the (euclidean) Dirac operator are expected to be described by a certain universality class of random matrix models. In particular, the latter predict the joint statistical distribution of the individual eigenvalues in any topological sector of the theory. We compare some of these predictions with high-precision numerical data obtained from quenched lattice QCD for a range of lattice spacings and volumes. While no complete matching is observed, the results agree with theoretical expectations at volumes larger than about 5 fm{sup 4}. (orig.)

  5. Lattice QCD in the {epsilon}-regime and random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Giusti, Leonardo; Luescher, Martin [CERN, Theory Division, Geneva (Switzerland)]. E-mail addresses: leonardo.giusti@cern.ch; luscher@mail.cern.ch; Weisz, Peter [Max-Planck-Institut fuer Physik, Munich (Germany)]. E-mail: pew@dmumpiwh.mppmu.mpg.de; Wittig, Hartmut [DESY, Theory Group, Hamburg (Germany)]. E-mail: hartmut.wittig@desy.de

    2003-11-01

    In the {epsilon}-regime of QCD the main features of the spectrum of the low-lying eigenvalues of the (euclidean) Dirac operator are expected to be described by a certain universality class of random matrix models. In particular, the latter predict the joint statistical distribution of the individual eigenvalues in any topological sector of the theory. We compare some of these predictions with high-precision numerical data obtained from quenched lattice QCD for a range of lattice spacings and volumes. While no complete matching is observed, the results agree with theoretical expectations at volumes larger than about 5 fm{sup 4}. (author)

  6. Lattice Study of the High Density State of SU(2)-QCD

    CERN Document Server

    Muroya, S; Nonaka, C

    2001-01-01

    We investigate high density state of SU(2) QCD by using Lattice QCD simulation with Wilson fermions. The ratio of fermion determinants is evaluated at each step of the Metropol is link update by Woodbury formula. At $\\beta=0.7$, and $\\kappa = 0.150$, we calculate the baryon number density, the Polyakov lines, and the energy density of gluon sector with chemical potential $\\mu$=0 to 0.8 on the $4^{3} \\times 12$ lattice. Behavior of the meson propagators and diquark propagators with finite chemical potential are also investigated.

  7. Improved staggered quark actions with reduced flavour symmetry violations for lattice QCD

    CERN Document Server

    Lagaë, J F

    1999-01-01

    We introduce a new class of actions for staggered quarks in lattice QCD which significantly reduce flavour symmetry violations in the pion mass spectrum. An action introduced by the MILC collaboration for the same purpose is seen to be a special case. We discus how such actions arise from a systematic attempt to reduce flavour symmetry violations in the weak coupling limit. It is shown that for quenched lattice QCD at 6/g^2=5.7, representative actions of this class give a considerable reduction in flavour symmetry violation over the standard staggered action, and a significant reduction over what is achieved by the MILC action.

  8. Chiral effective theory methods and their application to the structure of hadrons from lattice QCD

    Science.gov (United States)

    Shanahan, P. E.

    2016-12-01

    For many years chiral effective theory (ChEFT) has enabled and supported lattice QCD calculations of hadron observables by allowing systematic effects from unphysical lattice parameters to be controlled. In the modern era of precision lattice simulations approaching the physical point, ChEFT techniques remain valuable tools. In this review we discuss the modern uses of ChEFT applied to lattice studies of hadron structure in the context of recent determinations of important and topical quantities. We consider muon g-2, strangeness in the nucleon, the proton radius, nucleon polarizabilities, and sigma terms relevant to the prediction of dark-matter-hadron interaction cross-sections, among others.

  9. Chiral Effective Theory Methods and their Application to the Structure of Hadrons from Lattice QCD

    CERN Document Server

    Shanahan, P E

    2016-01-01

    For many years chiral effective theory (ChEFT) has enabled and supported lattice QCD calculations of hadron observables by allowing systematic effects from unphysical lattice parameters to be controlled. In the modern era of precision lattice simulations approaching the physical point, ChEFT techniques remain valuable tools. In this review we discuss the modern uses of ChEFT applied to lattice studies of hadron structure in the context of recent determinations of important and topical quantities. We consider muon g-2, strangeness in the nucleon, the proton radius, nucleon polarizabilities, and sigma terms relevant to the prediction of dark-matter-hadron interaction cross-sections, among others.

  10. Lattice QCD results on cumulant ratios at freeze-out

    CERN Document Server

    Karsch, Frithjof

    2016-01-01

    Ratios of cumulants of net proton-number fluctuations measured by the STAR Collaboration show strong deviations from a skellam distribution, which should describe thermal properties of cumulant ratios, if proton-number fluctuations are generated in equilibrium and a hadron resonance gas (HRG) model would provide a suitable description of thermodynamics at the freeze-out temperature. We present some results on sixth order cumulants entering the calculation of the QCD equation of state at non-zero values of the baryon chemical potential (mu_B) and discuss limitations on the applicability of HRG thermodynamics deduced from a comparison between QCD and HRG model calculations of cumulants of conserved charge fluctuations. We show that basic features of the $\\mu_B$-dependence of skewness and kurtosis ratios of net proton-number fluctuations measured by the STAR Collaboration resemble those expected from a O(mu_B^2) QCD calculation of the corresponding net baryon-number cumulant ratios.

  11. $N^*$ 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 $Q^2$.

  12. Charmonium dissociation and heavy quark transport in hot quenched lattice QCD

    CERN Document Server

    Ding, H -T; Kaczmarek, O; Karsch, F; Satz, H; Söldner, W

    2012-01-01

    We study the properties of charmonium states at finite temperature in quenched lattice QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that the S wave states disappear at about 1.5 Tc. The charm diffusion coefficient is estimated and found to be approximately 1/{\\pi}T at 1.5Tc {\\leq} T {\\leq} 3Tc.

  13. Charmonium dissociation and heavy quark transport in hot quenched lattice QCD

    Directory of Open Access Journals (Sweden)

    Ding H.-T.

    2014-04-01

    Full Text Available We study the properties of charmonium states at finite temperature in quenched lattice QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that the S wave states disappear at about 1.5 Tc. The charm diffusion coeffcient is estimated and found to be approximately 1/πT at 1.5Tc ≲ T ≲ 3Tc.

  14. Study of the $Z_c^+$ channel using lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Prelovsek, Sasa [Stefan Inst., Ljubljana; Lang, C. B. [Graz U.; Leskovec, Luka [Stefan Inst., Ljubljana; Mohler, Daniel [Fermilab

    2015-01-15

    Recently experimentalists have discovered several charged charmoniumlike hadrons Zc+ with unconventional quark content c¯cd¯u. We perform a search for Zc+ with mass below 4.2 GeV in the channel IG(JPC)=1+(1+-) using lattice QCD. The major challenge is presented by the two-meson states J/ψπ, ψ2Sπ, ψ1D

  15. Determination of Freeze-out Conditions from Lattice QCD Calculations

    CERN Document Server

    Karsch, Frithjof

    2012-01-01

    Freeze-out conditions in Heavy Ion Collisions are generally determined by comparing experimental results for ratios of particle yields with theoretical predictions based on applications of the Hadron Resonance Gas model. We discuss here how this model dependent determination of freeze-out parameters may eventually be replaced by theoretical predictions based on equilibrium QCD thermodynamics.

  16. Twenty-first Century Lattice Gauge Theory: Results from the QCD Lagrangian

    Energy Technology Data Exchange (ETDEWEB)

    Kronfeld, Andreas S.; /Fermilab

    2012-03-01

    Quantum chromodynamics (QCD) reduces the strong interactions, in all their variety, to an elegant nonabelian gauge theory. It clearly and elegantly explains hadrons at short distances, which has led to its universal acceptance. Since its advent, however, many of its long-distance, emergent properties have been believed to be true, without having been demonstrated to be true. This paper reviews a variety of results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian. This body of work sheds light on the origin of hadron masses, its interplay with dynamical symmetry breaking, as well as on other intriguing features such as the phase structure of QCD. In addition, nonperturbative QCD is quantitatively important to many aspects of particle physics (especially the quark flavor sector), nuclear physics, and astrophysics. This review also surveys some of the most interesting connections to those subjects.

  17. Statistical analysis and the equivalent of a Thouless energy in lattice QCD Dirac spectra

    CERN Document Server

    Guhr, T; Meyer, S; Wilke, T

    1999-01-01

    Random Matrix Theory (RMT) is a powerful statistical tool to model spectral fluctuations. This approach has also found fruitful application in Quantum Chromodynamics (QCD). Importantly, RMT provides very efficient means to separate different scales in the spectral fluctuations. We try to identify the equivalent of a Thouless energy in complete spectra of the QCD Dirac operator for staggered fermions from SU(2) lattice gauge theory for different lattice size and gauge couplings. In disordered systems, the Thouless energy sets the universal scale for which RMT applies. This relates to recent theoretical studies which suggest a strong analogy between QCD and disordered systems. The wealth of data allows us to analyze several statistical measures in the bulk of the spectrum with high quality. We find deviations which allows us to give an estimate for this universal scale. Other deviations than these are seen whose possible origin is discussed. Moreover, we work out higher order correlators as well, in particular ...

  18. Hard and thermal probes of QGP from the perspective of lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Heng-Tong

    2014-12-15

    In this talk I review the current status of lattice QCD results on the hard and thermal probes of QGP, including jet quenching parameters, the melting of quarkonia and open heavy flavors, thermal photon/dilepton rates, electrical conductivity as well as heavy quark diffusion coefficients.

  19. Gauge-invariant nonlocal quark condensates in QCD a new interpretation of the lattice results

    CERN Document Server

    Meggiolaro, E

    2000-01-01

    We study the asymptotic short-distance behaviour as well as the asymptotic large-distance behaviour of the gauge-invariant quark-antiquark nonlocal condensates in QCD. A comparison of some analytical results with the available lattice data is performed.

  20. Parallel Supercomputing PC Cluster and Some Physical Results in Lattice QCD

    Institute of Scientific and Technical Information of China (English)

    LUOXiang-Qian; MEIZhong-Hao; EricB.Gregory; YANGJie-Chao; WANGYu-Li; LINYin

    2003-01-01

    We describe the construction of a high performance parallel computer composed of PC components, present some physical results for light hadron and hybrid meson masses from lattice QCD. We also show that the smearing technique is very useful for improving the spectrum calculations.

  1. I = 1 and I = 2 π-π scattering phase shifts from Nf = 2 + 1 lattice QCD

    Science.gov (United States)

    Bulava, John; Fahy, Brendan; Hörz, Ben; Juge, Keisuke J.; Morningstar, Colin; Wong, Chik Him

    2016-09-01

    The I = 1 p-wave and I = 2 s-wave elastic π-π scattering amplitudes are calculated from a first-principles lattice QCD simulation using a single ensemble of gauge field configurations with Nf = 2 + 1 dynamical flavors of anisotropic clover-improved Wilson fermions. This ensemble has a large spatial volume V =(3.7 fm) 3, pion mass mπ = 230 MeV, and spatial lattice spacing as = 0.11 fm. Calculation of the necessary temporal correlation matrices is efficiently performed using the stochastic LapH method, while the large volume enables an improved energy resolution compared to previous work. For this single ensemble we obtain mρ /mπ = 3.350 (24), gρππ = 5.99 (26), and a clear signal for the I = 2 s-wave. The success of the stochastic LapH method in this proof-of-principle large-volume calculation paves the way for quantitative study of the lattice spacing effects and quark mass dependence of scattering amplitudes using state-of-the-art ensembles.

  2. Efficient SIMDization and Data Management of the Lattice QCD Computation on the Cell Broadband Engine

    Directory of Open Access Journals (Sweden)

    Khaled Z. Ibrahim

    2009-01-01

    Full Text Available Lattice Quantum Chromodynamic (QCD models subatomic interactions based on a four-dimensional discretized space–time continuum. The Lattice QCD computation is one of the grand challenges in physics especially when modeling a lattice with small spacing. In this work, we study the implementation of the main kernel routine of Lattice QCD that dominates the execution time on the Cell Broadband Engine. We tackle the problem of efficient SIMD execution and the problem of limited bandwidth for data transfers with the off-chip memory. For efficient SIMD execution, we present runtime data fusion technique that groups data processed similarly at runtime. We also introduce analysis needed to reduce the pressure on the scarce memory bandwidth that limits the performance of this computation. We studied two implementations for the main kernel routine that exhibit different patterns of accessing the memory and thus allowing different sets of optimizations. We show the attributes that make one implementation more favorable in terms of performance. For lattice size that is significantly larger than the local store, our implementation achieves 31.2 GFlops for single precision computations and 16.6 GFlops for double precision computations on the PowerXCell 8i, an order of magnitude better than the performance achieved on most general-purpose processors.

  3. Charm quark mass and D-meson decay constants from two-flavour lattice QCD

    CERN Document Server

    Heitger, Jochen; Schaefer, Stefan; Virotta, Francesco

    2013-01-01

    We present a computation of the charm quark's mass and the leptonic D-meson decay constants f_D and f_{D_s} in two-flavour lattice QCD with non-perturbatively O(a) improved Wilson 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_K) and pion masses ranging down to ~ 190 MeV at L*m_pi > 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties.

  4. I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD

    OpenAIRE

    Beane, Silas R.; Bedaque, Paulo F.; Orginos, Kostas; Savage, Martin J.

    2005-01-01

    We compute the I=2 pi-pi scattering length at pion masses of m_pi ~ 294, 348 and 484 MeV in fully-dynamical lattice QCD using Luscher's finite-volume method. The calculation is performed with domain-wall valence-quark propagators on asqtad-improved MILC configurations with staggered sea quarks at a single lattice spacing, b ~ 0.125 fm. Chiral perturbation theory is used to perform the extrapolation of the scattering length from lattice quark masses down to the physical value, and we find m_pi...

  5. Lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs)

    Science.gov (United States)

    Engelhardt, M.; Musch, B.; Bhattacharya, T.; Green, J. R.; Gupta, R.; Hägler, P.; Krieg, S.; Negele, J.; Pochinsky, A.; Schäfer, A.; Syritsyn, S.; Yoon, B.

    2016-03-01

    An ongoing program of evaluating TMD observables within Lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Data on the naively T-odd Sivers and Boer-Mulders effects as well as the transversity TMD are presented.

  6. Non-degenerate light quark masses from 2+1f lattice QCD+QED

    Energy Technology Data Exchange (ETDEWEB)

    Drury, Shane [Southampton U.; Blum, Thomas [RIKEN BNL; Hayakawa, Masashi [Nagoya U.; Izubuchi, Taku [RIKEN BNL; Sachrajda, Chris [Southampton U.; Zhou, Ran [Indiana U.

    2014-01-01

    We report on a calculation of the effects of isospin breaking in Lattice QCD+QED. This involves using Chiral Perturbation Theory with Electromagnetic corrections to find the renormalized, non-degenerate, light quark masses. The calculations are carried out on QCD ensembles generated by the RBC and UKQCD collaborations using Domain Wall Fermions and the Iwasaki and Iwasaki+DSDR Gauge Actions with unitary pion masses down to 170 MeV. Non-compact QED is treated in the quenched approximation. The simulations use a $32^3$ lattice size with $a^{-1}=2.28(3)$ GeV (Iwasaki) and 1.37(1) (Iwasaki+DSDR). This builds on previous work from the RBC/UKQCD collaboration with lattice spacing $a^{-1}=1.78(4)$ GeV.

  7. A Prediction of the B*_c mass in full lattice QCD

    CERN Document Server

    Gregory, E B; Follana, E; Gamiz, E; Kendall, I D; Lepage, G P; Na, H; Shigemitsu, J; Wong, K Y

    2009-01-01

    By using the Highly Improved Staggered Quark formalism to handle charm, strange and light valence quarks in full lattice QCD, and NRQCD to handle bottom valence quarks we are able to determine accurately ratios of the B meson vector-pseudoscalar mass splittings, in particular, (m(B*_c)-m(B_c))/(m(B*_s)-m(B_s)). We find this ratio to be 1.15(15), showing the `light' quark mass dependence of this splitting to be very small. Hence we predict m(B_c*) = 6.330(7)(2)(6) GeV where the first two errors are from the lattice calculation and the third from existing experiment. This is the most accurate prediction of a gold-plated hadron mass from lattice QCD to date.

  8. Generating SU(Nc) pure gauge lattice QCD configurations on GPUs with CUDA and OpenMP

    CERN Document Server

    Cardoso, Nuno

    2011-01-01

    The starting point of any lattice QCD computation is the generation of a Markov chain of gauge field configurations. Due to the large number of lattice links and due to the matrix multiplications, generating SU(Nc) lattice QCD configurations is a highly demanding computational task, requiring advanced computer parallel architectures such as clusters of several Central Processing Units (CPUs) or Graphics Processing Units (GPUs). In this paper we present and explore the performance of CUDA codes for NVIDIA GPUs to generate SU(Nc) lattice QCD pure gauge configurations. Our implementation in one GPU uses CUDA and in multiple GPUs uses OpenMP and CUDA. We present optimized CUDA codes SU(2), SU(3) and SU(4). We also show a generic SU(Nc) code for Nc$\\,\\geq 4$ and compare it with the optimized version of SU(4). Our codes are publicly available for free use by the lattice QCD community.

  9. Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method

    CERN Document Server

    Iritani, Takumi

    2016-01-01

    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 b...

  10. Searching for the CEP location with nonlocal PNJL models constrained by Lattice QCD

    CERN Document Server

    Contrera, Gustavo A; Blaschke, David

    2016-01-01

    We investigate the possible location of the critical end point 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 $\\Delta P / T^4$ vs $T/T_c$ with lattice QCD results shows a better agreement when Lorentzian formfactors 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 on 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 supports the existence of a critical point and favors for its location the region $69.9~{\\rm MeV}\\le T_{\\rm CEP} \\le...

  11. 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.)

  12. Nucleon isovector couplings from $N_f=2$ lattice QCD

    CERN Document Server

    Bali, Gunnar S; Glässle, Benjamin; Göckeler, Meinulf; Najjar, Johannes; Rödl, Rudolf H; Schäfer, Andreas; Schiel, Rainer W; Söldner, Wolfgang; Sternbeck, Andre

    2014-01-01

    We compute the axial, scalar, tensor and pseudoscalar isovector couplings of the nucleon as well as the induced tensor and pseudoscalar charges in lattice simulations with $N_f=2$ mass-degenerate non-perturbatively improved Wilson-Sheikholeslami-Wohlert fermions. The simulations are carried out down to a pion mass of 150 MeV and linear spatial lattice extents of up to 4.6 fm at three different lattice spacings ranging from approximately 0.08 fm to 0.06 fm. Possible excited state contamination is carefully investigated and finite volume effects are studied. The couplings, determined at these lattice spacings, are extrapolated to the physical pion mass. In this limit we find agreement with experimental results, where these exist, with the exception of the magnetic moment. A proper continuum limit could not be performed, due to our limited range of lattice constants, but no significant lattice spacing dependence is detected. Upper limits on discretization effects are estimated and these dominate the error budget...

  13. Lattice QCD studies on baryon interactions from L\\"uscher's finite volume method and HAL QCD method

    CERN Document Server

    Iritani, Takumi

    2015-01-01

    A comparative study between the L\\"uscher's finite volume method and the time-dependent HAL QCD method is given for the $\\Xi\\Xi$($^1\\mathrm{S}_0$) interaction as an illustrative example. By employing the smeared source and the wall source for the interpolating operators, we show that the effective energy shifts $\\Delta E_{\\rm eff} (t)$ in L\\"uscher's method do not agree between different sources, yet both exhibit fake plateaux. On the other hand, the interaction kernels $V(\\vec{r})$ obtained from the two sources in the HAL QCD method agree with each other already for modest values of $t$. We show that the energy eigenvalues $\\Delta E(L)$ in finite lattice volumes ($L^3$) calculated by $V(\\vec{r})$ indicate that there is no bound state in the $\\Xi\\Xi(^1\\mathrm{S}_0)$ channel at $m_{\\pi}=0.51$ GeV in 2+1 flavor QCD.

  14. The IR sector of QCD: lattice versus Schwinger-Dyson equations

    CERN Document Server

    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.

  15. The IR sector of QCD: lattice versus Schwinger-Dyson equations

    Science.gov (United States)

    Binosi, Daniele

    2010-12-01

    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.

  16. Coupled channel approach to strangeness S = -2 baryon-bayron interactions in Lattice QCD

    CERN Document Server

    Sasaki, Kenji; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko

    2015-01-01

    The baryon-baryon interactions with strangeness S = -2 with the flavor SU(3) breaking are calculated for the first time by using the HAL QCD method extended to coupled channel system in lattice QCD. The potential matrices are extracted from the Nambu-Bethe-Salpeter wave functions obtained by the 2+1 flavor gauge configurations of CP-PACS/JLQCD Collaborations with a physical volume of 1.93 fm cubed and with m_pi/m_K = 0.96, 0.90, 0.86. The spatial structure and the quark mass dependence of the potential matrix in the baryon basis and in the SU(3) basis are investigated.

  17. Lattice QCD simulations using the OpenACC platform

    Science.gov (United States)

    Majumdar, Pushan

    2016-10-01

    In this article we will explore the OpenACC platform for programming Graphics Processing Units (GPUs). The OpenACC platform offers a directive based programming model for GPUs which avoids the detailed data flow control and memory management necessary in a CUDA programming environment. In the OpenACC model, programs can be written in high level languages with OpenMP like directives. We present some examples of QCD simulation codes using OpenACC and discuss their performance on the Fermi and Kepler GPUs.

  18. Light Meson Physics from Maximally Twisted Mass Lattice QCD

    CERN Document Server

    Baron, R; Dimopoulos, P; Farchioni, F; Frezzotti, R; Gimenez, V; Herdoiza, G; Jansen, K; Lubicz, V; Michael, C; Muenster, G; Palao, D; Rossi, G C; Scorzato, L; Shindler, A; Simula, S; Sudmann, T; Urbach, C; Wenger, U

    2009-01-01

    We present a comprehensive investigation of light meson physics using maximally twisted mass fermions for two mass-degenerate quark flavours. By employing four values of the lattice spacing, spatial lattice extents ranging from 2.0 fm to 2.5 fm and pseudo scalar masses in the range 280 MeV to 650 MeV we control the major systematic effects of our calculation. This enables us to confront our data with chiral perturbation theory and extract low energy constants of the effective chiral Lagrangian and derived quantities, such as the light quark mass, with high precision.

  19. K$\\to \\pi\\pi$ Amplitudes from Lattice QCD with a Light Charm Quark

    CERN Document Server

    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.

  20. QCD at finite temperature and density on the lattice

    Directory of Open Access Journals (Sweden)

    Lombardo M.-P.

    2010-10-01

    Full Text Available In the first lecture we briefly summarize the basics of field theory thermodynamics and critical phenomena. We then introduce the lattice gauge field theory approach to QCD at finite temperature and density, which is a non-perturbative scheme allowing first principle calculations using the QCD Lagrangian as a sole input. Some of the general concepts and idea introduced at the beginning are demonstrated by use of simple effective models of QCD. The second lecture is devoted to applications. We emphasize that current methods suffice to study the main phenomena at RHIC and LHC energies, and we discuss the ongoing theoretical efforts devoted to the solution of the sign problem which hampers the simulations of cold and dense matter. We conclude with short overview of the status of the field as of Summer 2008.

  1. Vortex liquid in magnetic-field-induced superconducting vacuum of quenched lattice QCD

    CERN Document Server

    Braguta, V V; Chernodub, M N; Kotov, A Yu; Polikarpov, M I

    2013-01-01

    In the background of the strong magnetic field the vacuum is suggested to possess an electromagnetically superconducting phase characterised by the emergence of inhomogeneous quark-antiquark vector condensates which carry quantum numbers of the charged rho mesons. The rho-meson condensates are inhomogeneous due to the presence of the stringlike defects ("the rho vortices") which are parallel to the magnetic field (the superconducting vacuum phase is similar to the mixed Abrikosov phase of a type-II superconductor). In agreement with these expectations, we have observed the presence of the rho vortices in numerical simulations of the vacuum of the quenched two-color lattice QCD in strong magnetic field background. We have found that in the quenched QCD the rho vortices form a liquid. The transition between the usual (insulator) phase at low B and the superconducting vortex liquid phase at high B turns out to be very smooth, at least in the quenched QCD.

  2. Isospin splittings of meson and baryon masses from three-flavor lattice QCD + QED

    Science.gov (United States)

    Horsley, R.; Nakamura, Y.; Perlt, H.; Pleiter, D.; Rakow, P. E. L.; Schierholz, G.; Schiller, A.; Stokes, R.; Stüben, H.; Young, R. D.; Zanotti, J. M.

    2016-10-01

    Lattice QCD simulations are now reaching a precision where isospin breaking effects become important. Previously, we have developed a program to systematically investigate the pattern of flavor symmetry beaking within QCD and successfully applied it to meson and baryon masses involving up, down and strange quarks. In this Letter we extend the calculations to QCD + QED and present our first results on isospin splittings in the pseudoscalar meson and baryon octets. In particular, we obtain the nucleon mass difference of {M}n-{M}p=1.35(18)(8){{MeV}} and the electromagnetic contribution to the pion splitting {M}{π +}-{M}{π 0}=4.60(20){{MeV}}. Further we report first determination of the separation between strong and electromagnetic contributions in the \\overline{{MS}} scheme.

  3. Lattice study of ChPT beyond QCD

    CERN Document Server

    Appelquist, Thomas; Babich, Ron; Brower, Richard C; Cheng, Michael; Clark, Michael A; Cohen, Saul D; Fleming, George T; Kiskis, Joseph; Neil, Ethan T; Osborn, James C; Rebbi, Claudio; Schaich, David; Vranas, Pavlos

    2010-01-01

    We describe initial results by the Lattice Strong Dynamics (LSD) collaboration of a study into the variation of chiral properties of chiral properties of SU(3) Yang-Mills gauge theory as the number of massless flavors changes from $N_f = 2$ to $N_f = 6$, with a focus on the use of chiral perturbation theory.

  4. Lattice QCD Production on a Commodity Cluster at Fermilab

    Institute of Scientific and Technical Information of China (English)

    D.Holmgren; P.Mackenzie; 等

    2001-01-01

    Large scale QCD Monte Carlo calculations have typically been performed on either commercial supercomputers or specially built massively parallel computers such as Fermilab's ACPMAPS.Commodity clusters equipped with high performance networking equipment present an attractive alternative,achieving superior performance to price ratios and offering clear upgrade paths.We describe the construction and results to date of Fermilab's prototype production cluster,which consists of 80 dual Pentium Ⅲsystems interconnected with Myrinet networking hardware.We describe software tools and techniques we have developed for operating system installation and administration.We discuss software optimizations using the Pentium's built-in parallel computation facilities(SSE),Finally,we present short and long term plans for the construction of larger facilities.

  5. The phase-shift of isospin-2 pi-pi scattering from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Jozef J. Dudek, Robert G. Edwards, Michael J. Peardon, David G. Richards, Christopher E. Thomas

    2011-04-01

    Finite-volume lattice QCD calculations offer the possibility of extracting resonance parameters from the energy-dependent elastic phase-shift computed using the L\\"uscher technique. In this letter, as a trial of the method, we report on the extraction of the non-resonant phase-shift for $S$ and $D$-wave $\\pi\\pi$ isospin-2 scattering from dynamical lattice QCD computations. We define a variational basis of operators resembling pairs of pions of definite relative momentum and extract a spectrum of excited states that maps to phase-shifts at a set of discrete scattering momenta. Computations are performed with pion masses between $400$ and $520$ MeV on multiple spatial volumes. We observe no significant quark mass dependence in the phase-shifts extracted which are in reasonable agreement with the available experimental data at low momentum.

  6. Neutral $B$ mixing from $2+1$ flavor lattice-QCD: the Standard Model and beyond

    CERN Document Server

    Bouchard, C M; Bernard, C; El-Khadra, A X; Gamiz, E; Kronfeld, A S; Laiho, J; Van de Water, R S

    2011-01-01

    We report on the status of our lattice-QCD calculation of the hadronic contribution to $B_d^0$ and $B^0_s$ mixing, with $2+1$ flavors of dynamical sea quarks. Preliminary results for hadronic mixing matrix elements are given for a basis of five four-quark, dimension-six, $\\Delta B=2$ mixing operators that spans the space of all possible hadronic mixing contributions in the Standard Model and beyond. At the intermediate stage of analysis reported on in this work, our errors are competitive with published Standard Model matrix element results. For beyond the Standard Model matrix elements, this is the first unquenched calculation and the first new lattice-QCD calculation in ten years.

  7. The U(1)A anomaly in high temperature QCD with chiral fermions on the lattice

    CERN Document Server

    Sharma, Sayantan; Karsch, Frithjof; Laermann, Edwin; Mukherjee, Swagato

    2015-01-01

    The magnitude of the $U_A(1)$ symmetry breaking is expected to affect the nature of $N_f=2$ QCD chiral phase transition. The explicit breaking of chiral symmetry due to realistic light quark mass is small, so it is important to use chiral fermions on the lattice to understand the effect of $U_A(1)$ near the chiral crossover temperature, $T_c$. We report our latest results for the eigenvalue spectrum of 2+1 flavour QCD with dynamical Mobius domain wall fermions at finite temperature probed using the overlap operator on $32^3\\times 8$ lattice. We check how sensitive the low-lying eigenvalues are to the sea-light quark mass. We also present a comparison with the earlier independent results with domain wall fermions.

  8. Thermo-magnetic effects in quark matter: Nambu-Jona-Lasinio model constrained by lattice QCD

    CERN Document Server

    Farias, R L S; Avancini, S S; Pinto, M B; Krein, G

    2016-01-01

    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 a G(B, T) are compared with the ones obtained at constant coupling G. The model with a 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 running coupling can be easily implemented to improve typical model applications to magnetized quark matter.

  9. Scalar Glueball-qqbar Mixing above 1 GeV and implications for Lattice QCD

    CERN Document Server

    Close, Francis Edwin

    2001-01-01

    Lattice QCD predictions have motivated several recent studies of the mixing between the predicted JPC = 0++ glueball and a qqbar nonet in the 1.3 to 1.7 GeV region. We show that results from apparently different approaches have some common features, explain why this is so and abstract general conclusions. We place particular emphasis on the flavour dependent constraints imposed by decays of the f0(1370), f0(1500) and f0(1700) to all pairs of pseudoscalar mesons. From these results we identify a systematic correlation between glueball mass, mixing, and flavour symmetry breaking and conclude that the glueball may be rather lighter than some quenched lattice QCD computations have suggested. We identify experimental tests that can determine the dynamics of a glueball in this mass region and discuss quantitatively the feasibility of decoding glueball-qqbar mixing.

  10. The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory

    Energy Technology Data Exchange (ETDEWEB)

    Calle Cordon, Alvaro C. [JLAB; DeGrand, Thomas A. [University of Colorado; Goity, Jose L. [JLAB

    2014-07-01

    Baryon masses at varying values of Nc and light quark masses are studied with Lattice QCD and the results are analyzed in a low energy effective theory based on a combined framework of the 1/Nc and Heavy Baryon Chiral Perturbation Theory expansions. Lattice QCD results for Nc=3, 5 and 7 obtained in quenched calculations, as well as results for unquenched calculations for Nc=3, are used for the analysis. The results are consistent with a previous analysis of Nc=3 LQCD results, and in addition permit the determination of sub-leading in 1/Nc effects in the spin-flavor singlet component of the baryon masses as well as in the hyperfine splittings.

  11. Minkowski space pion model inspired by lattice QCD running quark mass

    Science.gov (United States)

    Mello, Clayton S.; de Melo, J. P. B. C.; Frederico, T.

    2017-03-01

    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.

  12. 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.

  13. 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.

  14. Results and Perspectives in HEP, vis-a-vis Lattice QCD

    CERN Document Server

    Mangano, Michelangelo L

    2000-01-01

    I review in this presentation some aspects of phenomenology in High Energy Physics which are related to recent and possibly future progress in lattice QCD. In particular, I cover (i) the extraction of CKM matrix elements from B physics, (ii) the determination of epsilon'/epsilon, as well as (iii) some issues emerged in the physics of high energy jets produced in hadronic collisions, where input from non-perturbative calculations would benefit our capability to perform better theoretical predictions.

  15. Quasiparticle Description of the QCD Plasma, Comparison with Lattice Results at Finite T and Mu

    CERN Document Server

    Szabó, K K

    2003-01-01

    We compare our 2+1 flavor, staggered QCD lattice results with a quasiparticle picture. We determine the pressure, the energy density, the baryon density, the speed of sound and the thermal masses as a function of T and $\\mu_B$. For the available thermodynamic quantities the difference is a few percent between the results of the two approaches. We also give the phase diagram on the $\\mu_B$--T plane and estimate the critical chemical potential at vanishing temperature.

  16. Study of lattice QCD at finite chemical potential using canonical ensemble approach

    CERN Document Server

    Bornyakov, V G; Goy, V A; Molochkov, A V; Nakamura, Atsushi; Nikolaev, A A; Zakharov, V I

    2016-01-01

    New approach to computation of canonical partition functions in $N_f=2$ lattice QCD is presented. We compare results obtained by new method with results obtained by known method of hopping parameter expansion. We observe agreement between two methods indicating validity of the new method. We use results for the number density obtained in the confining and deconfining phases at imaginary chemical potential to determine the phase transition line at real chemical potential.

  17. Wilson flow and scale setting from lattice QCD

    CERN Document Server

    Bornyakov, V G; Hudspith, R; Nakamura, Y; Perlt, H; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Stüben, H; Zanotti, J M

    2015-01-01

    We give a determination of the phenomenological value of the Wilson (or gradient) flow scales t0 and w0 for 2+1 flavours of dynamical quarks. The simulations are performed keeping the average quark mass constant, which allows the approach to the physical point to be made in a controlled manner. O(a) improved clover fermions are used and together with four lattice spacings this allows the continuum extrapolation to be taken.

  18. Semileptonic B → D** decays in lattice QCD: a feasability

    Energy Technology Data Exchange (ETDEWEB)

    Atoui, M.; Morenas, V. [Unite Mixte de Recherche 6533 CNRS/IN2P3, Universite Blaise Pascal, Laboratoire de Physique Corpusculaire de Clermont-Ferrand, Campus des Cezeaux, 24 avenue des Landais, BP 80026, Aubiere Cedex (France); Blossier, B.; Pene, O. [Unite Mixte de Recherche 8627 du Centre National de la Recherche Scientifique et Universite Paris-Sud XI, Laboratoire de Physique Theorique, Orsay Cedex (France); Petrov, K. [Inria Saclay, Batiment Alan Turing, Palaiseau (France)

    2015-08-15

    We compute the decays B → D{sub 0}{sup *} and B → D{sub 2}{sup *} with finite masses for the b and c quarks. We first discuss the spectral properties of both the B meson as a function of its momentum and the D{sub 0}{sup *} and D{sub 2}{sup *} at rest. We compute the theoretical formulae leading to the decay amplitudes from the three-point and two-point correlators. We then compute the amplitudes at zero recoil of B → D{sub 0}{sup *}, which turns out not to be vanishing contrary to what happens in the heavy quark limit. This opens the possibility to get better agreement with experiment. To improve the continuum limit we have added a set of data with smaller lattice spacing. The B → D{sub 2}{sup *} vanishes at zero recoil and we show a convincing signal but only slightly more than 1 sigma from 0. In order to reach quantitatively significant results we plan to exploit fully smaller lattice spacings as well as another lattice regularisation. (orig.)

  19. The gluon momentum fraction of the nucleon from lattice QCD

    CERN Document Server

    Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Jansen, Karl; Panagopoulos, Haralambos; Wiese, Christian

    2016-01-01

    We perform a direct calculation of the gluon momentum fraction of the nucleon using maximally twisted mass fermion ensembles with $N_f=2+1+1$ flavors at a pion mass of about $370\\,\\mathrm{MeV}$ and a lattice spacing of $a\\approx 0.082\\,\\mathrm{fm}$ and with $N_f=2$ flavors at the physical pion mass and a lattice spacing of $a\\approx 0.093\\,\\mathrm{fm}$. In the definition of the gluon operator we employ stout smearing to obtain a statistically significant result for the bare matrix elements. In addition, we perform a lattice perturbative calculation including 2 levels of stout smearing to carry out the mixing and the renormalization of the quark and gluon operators. We find, after conversion to the $\\overline{\\mathrm{MS}}$ scheme at a scale of $2\\,\\mathrm{GeV}$: $\\langle x\\rangle^R_g {=} 0.284(23)(23)$ for pion mass of about $370\\,\\mathrm{MeV}$ and $\\langle x\\rangle^R_g {=} 0.283(23)(15)$ for the physical pion mass.

  20. Leading hadronic contributions to the running of the electroweak coupling constants from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Florian [OakLabs GmbH, Hennigsdorf (Germany); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Petschlies, Marcus [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik; Pientka, Grit [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik

    2015-12-15

    The quark-connected leading-order hadronic contributions to the running of the electromagnetic fine structure constant, α{sub QED}, and the weak mixing angle, θ{sub 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.

  1. Spectral density analysis of time correlation functions in lattice QCD using the maximum entropy method

    CERN Document Server

    Fiebig, H R

    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 practical issues of the approach.

  2. Decay constants and spectroscopy of mesons in lattice QCD using domain-wall fermions

    CERN Document Server

    Fahy, B; Hashimoto, S; Kaneko, T; Noaki, J; Tomii, M

    2015-01-01

    We report results of masses and decay constants of light and charmed pseudo-scalar mesons using lattice QCD with M\\"obius domain-wall fermions. Using this formulation we are able to compute pseudo-scalar decay constants through the pseudo-scalar density operator as well as with the axial-vector current. Results are shown from several lattice spacings and pion masses between 230 MeV and 500 MeV. We present an analysis of these results at different quark masses to show the chiral properties of the light mesons masses and decay constants.

  3. 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.

  4. Nucleon form factors and moments of parton distributions in twisted mass lattice QCD

    CERN Document Server

    Alexandrou, C; Carbonell, J; Constantinou, M; Guichon, P; Harraud, P A; Jansen, K; Kallidonis, C; Korzec, T; Papinutto, M

    2012-01-01

    We present results on the electroweak form factors and on the lower moments of parton distributions of the nucleon, within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Results are obtained 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 by comparing results 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 non-perturbatively and the values are given in the MS-scheme at a scale mu=2 GeV.

  5. Finite-volume Hamiltonian method for coupled channel interactions in lattice QCD

    CERN Document Server

    Wu, Jia-Jun; Thomas, A W; Young, R D

    2014-01-01

    Within a multi-channel formulation of $\\pi\\pi$ scattering, we investigate the use of the finite-volume Hamiltonian approach to relate lattice QCD spectra to scattering observables. The equivalence of the Hamiltonian approach and the coupled-channel extension of the well-known L\\"uscher formalism is established. Unlike the single channel system, the spectra at a single lattice volume in the coupled channel case do not uniquely determine the scattering parameters. We investigate the use of the Hamiltonian framework as a method to directly fit the lattice spectra and thereby extract the scattering phase shifts and inelasticities. We find that with a modest amount of lattice data, the scattering parameters can be reproduced rather well, with only a minor degree of model dependence.

  6. 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.

  7. The pi+ pi+ scattering length from maximally twisted mass lattice QCD

    CERN Document Server

    Feng, Xu; Renner, Dru B

    2009-01-01

    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_pi a_pipi(I=2)=-0.04385(28)(38) for the scattering length, where the first error is statistical and the second is our estimate of several systematic effects.

  8. Neutron and proton electric dipole moments from Nf=2 +1 domain-wall fermion lattice QCD

    Science.gov (United States)

    Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Soni, Amarjit; Rbc; Ukqcd Collaborations

    2016-05-01

    We present a lattice calculation of the neutron and proton electric dipole moments (EDMs) with Nf=2 +1 flavors of domain-wall fermions. The neutron and proton EDM form factors are extracted from three-point functions at the next-to-leading order in the θ vacuum of QCD. In this computation, we use pion masses of 0.33 and 0.42 GeV and 2.7 fm3 lattices with Iwasaki gauge action, and a 0.17 GeV pion and a 4.6 fm3 lattice with I-DSDR gauge action, all generated by the RBC and UKQCD collaborations. The all-mode averaging technique enables an efficient and high statistics calculation. Chiral behavior of lattice EDMs is discussed in the context of baryon chiral perturbation theory. In addition, we also show numerical evidence on the relationship of three- and two-point correlation functions with the local topological charge distribution.

  9. Precision charmonium and D physics from lattice QCD and determination of the charm quark mass

    CERN Document Server

    Davies, C T H

    2008-01-01

    I will describe recent results from the HPQCD collaboration using a new very accurate method for charm quarks in lattice QCD, that we have used in calculations including the full effect of u, d and s sea quarks. Multiple values of the lattice spacing and of the u, d and s sea quark masses allow us to extrapolate reliably, with a full error budget, to the real world. This opens up the field of charm physics to precision lattice QCD tests. So far we have calculated the D and D_s meson masses to 6 MeV, having fixed the charm quark mass from the eta_c meson. Our D and D_s decay constants (determined to 2%) make an interesting comparison to CLEO-c results as we await improved experimental errors. We are also able to determine the charm quark mass to an accuracy of 1% using charmonium correlators and high-order continuum QCD perturbation theory. Future calculations are briefly discussed.

  10. Finite volume treatment of pi pi scattering and limits to phase shifts extraction from lattice QCD

    CERN Document Server

    Albaladejo, M; Oset, E; Rios, G; Roca, L

    2012-01-01

    We study theoretically the effects of finite volume for pipi scattering in order to extract physical observables for infinite volume from lattice QCD. We compare three different approaches for pipi scattering (lowest order Bethe-Salpeter approach, N/D and inverse amplitude methods) with the aim to study the effects of the finite size of the box in the potential of the different theories, specially the left-hand cut contribution through loops in the crossed t,u-channels. We quantify the error made by neglecting these effects in usual extractions of physical observables from lattice QCD spectra. We conclude that for pipi phase-shifts in the scalar-isoscalar channel up to 800 MeV this effect is negligible for box sizes bigger than 2.5m_pi^-1 and of the order of 5% at around 1.5-2m_pi^-1. For isospin 2 the finite size effects can reach up to 10% for that energy. We also quantify the error made when using the standard Luscher method to extract physical observables from lattice QCD, which is widely used in the lite...

  11. Lee-Yang zeros analysis of finite density lattice QCD

    CERN Document Server

    Crompton, P

    2001-01-01

    coefficients from different ensembles (through the ratio of the normalisations) we are thus able to alleviate the bias in our sampling. We then further develop this method for SU(3) with static quarks by generating a range of canonical ensembles which we combine with our new re-weighting approach. From our SU(2) measurements we establish the existence of a diquark superfluid at high densities and low temperatures. We also determine the position and order of the associated symmetry breaking transitions in the mass - chemical potential plane. From our measurements of static SU(3) we establish that the finite density transition at intermediate coupling is a first order percolation transition. Having addressed the pathologies of the re-weighting method in two nonabelian gauge field theories which are simpler to evaluate numerically, in future work SU(3) QCD can be evaluated at finite density. Recent results from four-fermion interaction models have suggested that new exotic phases form at finite baryon density wh...

  12. Excited-State Effective Masses in Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    George Fleming, Saul Cohen, Huey-Wen Lin

    2009-10-01

    We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.

  13. Lattice study of large $N_c$ QCD

    CERN Document Server

    DeGrand, Thomas

    2016-01-01

    We present a lattice simulation study of large $N_c$ regularities of meson and baryon spectroscopy in $SU(N_c)$ gauge theory with two flavors of dynamical fundamental representation fermions. Systems investigated include $N_c=2$, 3, 4, and 5, over a range of fermion masses parametrized by a squared pseudoscalar to vector meson mass ratio between about 0.2 to 0.7. Good agreement with large $N_c$ scaling is observed in the static potential, in meson masses and decay constants, and in baryon spectroscopy.

  14. Heavy Quark diffusion from lattice QCD spectral functions

    CERN Document Server

    Ding, H -T; Kaczmarek, O; Karsch, F; Satz, H; Soeldner, W

    2011-01-01

    We analyze the low frequency part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region $1.5\\lesssim T/T_c\\lesssim 3$ as well as for $T \\simeq 0.75T_c$. We present evidence for the existence of a transport peak above $T_c$ and its absence below $T_c$. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation we also determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium.

  15. CP violation and Kaon weak matrix elements from Lattice QCD

    CERN Document Server

    Garron, Nicolas

    2015-01-01

    In this short review, I present the recent lattice computations of kaon weak matrix elements relevant to $K \\to \\pi\\pi$ decays and neutral kaon mixing. These matrix elements are key to the theoretical determination of the CP violation parameters $\\epsilon$ and $\\epsilon'$ . Impressive progress have been achieved recently, in particular the first realistic computation of $\\epsilon'/\\epsilon$ with physical kinematics has been reported in [1]. The novelty is the $\\Delta I = 1/2$ channel, whereas the $\\Delta I = 3/2$ contribution is now computed at several values of the lattice spacing and extrapolated to the continuum limit. I will also present the status of $B_K$ and discuss its error budget, with a particular emphasis on the perturbative error. Finally I will review the matrix elements of neutral kaon mixing beyond the standard model and will argue that the discrepancy observed by different collaborations could be explained by the renormalisation procedure of the relevant four-quark operators.

  16. Thermodynamics of lattice QCD with two light quark flavours on A 16{sup 3} x 8 lattice II.

    Energy Technology Data Exchange (ETDEWEB)

    Gottlieb, S.; Heller, U. M.; Kennedy, A. D.; Kim, S.; Kogut, J. B.; Liu, C.; Renken, R. L.; Sinclair, D. K.; Sugar, R. L.; Toussaint, D.; Wang, K. C.; High Energy Physics; Indiana Univ.; Florida State Univ.; Seoul National Univ.; Univ. of Illinois; Morgan Stanley & Co. Inc.; Univ. of Central Florida; Univ. of California; Univ. of Arizona; China Graduate School of Theology

    1997-01-01

    We have extended our earlier simulations of the high-temperature behavior of lattice QCD with two light flavors of staggered quarks on a 16{sup 3}x8 lattice to a lower quark mass (m{sub q}=0.00625). The transition from hadronic matter to a quark-gluon plasma is observed at 6/g{sup 2}=5.49(2) corresponding to a temperature of {Tc}{approx}140 MeV. We present measurements of observables which probe the nature of the quark-gluon plasma and serve to distinguish it from hadronic matter. Although the transition is quite abrupt, we have seen no indications that it is first order.

  17. Thermodynamics of lattice QCD with two light quarks on a 16{sup 3}{times}8 lattice. II

    Energy Technology Data Exchange (ETDEWEB)

    Gottlieb, S. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States); Heller, U.M.; Kennedy, A.D. [SCRI, The Florida State University, Tallahassee, Florida 32306-4052 (United States); Kim, S. [Center for Theoretical Physics, Seoul National University, Seoul (Korea); Kogut, J.B. [Department of Physics, University of Illinois, 1110 West Green Street, Urbana, Illinois 61801 (United States); Liu, C. [Morgan Stanley and Co. Inc., 1585 Broadway, New York, New York 10036 (United States); Renken, R.L. [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Sinclair, D.K. [HEP Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Sugar, R.L. [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Toussaint, D. [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Wang, K.C. [China Graduate School of Theology, 5 Devon Rd, Kowloon Tong, Kowloon (Hong Kong)

    1997-06-01

    We have extended our earlier simulations of the high-temperature behavior of lattice QCD with two light flavors of staggered quarks on a 16{sup 3}{times}8 lattice to a lower quark mass (m{sub q}=0.00625). The transition from hadronic matter to a quark-gluon plasma is observed at 6/g{sup 2}=5.49(2) corresponding to a temperature of T{sub c}{approx}140 MeV. We present measurements of observables which probe the nature of the quark-gluon plasma and serve to distinguish it from hadronic matter. Although the transition is quite abrupt, we have seen no indications that it is first order. {copyright} {ital 1997} {ital The American Physical Society}

  18. Resonance Parameters of the Rho-Meson from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Xu Feng, Karl Jansen, Dru Renner

    2011-05-01

    We perform a non-perturbative lattice calculation of the P-wave pion-pion scattering phase in the rho-meson decay channel using two flavors of maximally twisted mass fermions at pion masses ranging from 480 MeV to 290 MeV. Making use of finite-size methods, we evaluate the pion-pion scattering phase in the center-of-mass frame and two moving frames. Applying an effective range formula, we find a good description of our results for the scattering phase as a function of the energy covering the resonance region. This allows us to extract the rho-meson mass and decay width and to study their quark mass dependence.

  19. Resonance parameters of the {rho}-meson from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xu [DESY, Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Jansen, Karl; Renner, Dru B. [DESY, Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC

    2010-12-15

    We perform a non-perturbative lattice calculation of the P-wave pion-pion scattering phase in the {rho}-meson decay channel using two flavors of maximally twisted mass fermions at pion masses ranging from 480 MeV to 290 MeV. Making use of finite-size methods, we evaluate the pion-pion scattering phase in the center-of-mass frame and two moving frames. Applying an effective range formula, we find a good description of our results for the scattering phase as a function of the energy covering the resonance region. This allows us to extract the {rho}-meson mass and decay width and to study their quark mass dependence. (orig.)

  20. Quark Propagation in the Instantons of Lattice QCD

    CERN Document Server

    Trewartha, Daniel; Leinweber, Derek; Roberts, Dale S

    2013-01-01

    We quantitatively examine the extent to which instanton degress of freedom, contained within standard Monte-carlo generated gauge-field configurations, can maintain the characteristic features of the mass and renormalisation functions of the non-perturbative quark propagator. We use over-improved stout-link smearing to isolate instanton effects on the lattice. Using a variety of measures, we illustrate how gauge fields consisting almost solely of instanton-like objects are produced after only 50 sweeps of smearing. We find a full vacuum, with a packing fraction more than three times larger than phenomenological models predict. We calculate the overlap quark propagator on these smeared configurations, and find that even at high levels of smearing the majority of the characteristic features of the propagator are reproduced. We thus conclude that instantons contained within standard Monte-carlo generated gauge-field configurations are the degrees of freedom responsible for the dynamical generation of mass observ...

  1. Neutral B mixing from 2+1 flavor lattice QCD

    CERN Document Server

    Freeland, E D; Bernard, C; El-Khadra, A X; Gamiz, E; Kronfeld, A S; Laiho, J; Van de Water, R S

    2012-01-01

    We present an update of the Fermilab-MILC Collaboration's calculation of hadronic matrix elements for B^0-\\bar{B^0} mixing. This work is a more extended analysis than our recent publication of the SU(3)-breaking ratio xi [arXiv:1205.7013]. We use the asqtad staggered action for light valence quarks in combination with the Fermilab interpretation of the Sheikoleslami-Wohlert action for heavy quarks. The calculations use MILC's 2+1 flavor asqtad ensembles. Ensembles include four lattice spacings from approximately 0.125 fm to 0.045 fm and up/down to strange quark mass ratios as low as 0.05. Our calculation covers the complete set of five operators needed to describe B mixing in the Standard Model and beyond. In addition to an update including a fuller set of analyzed data, we comment on the form of the staggered ChPT extrapolation function.

  2. Dipolar matter-wave solitons in two-dimensional anisotropic discrete lattices

    Science.gov (United States)

    Chen, Huaiyu; Liu, Yan; Zhang, Qiang; Shi, Yuhan; Pang, Wei; Li, Yongyao

    2016-05-01

    We numerically demonstrate two-dimensional (2D) matter-wave solitons in the disk-shaped dipolar Bose-Einstein condensates (BECs) trapped in strongly anisotropic optical lattices (OLs) in a disk's plane. The considered OLs are square lattices which can be formed by interfering two pairs of plane waves with different intensities. The hopping rates of the condensates between two adjacent lattices in the orthogonal directions are different, which gives rise to a linearly anisotropic system. We find that when the polarized orientation of the dipoles is parallel to disk's plane with the same direction, the combined effects of the linearly anisotropy and the nonlocal nonlinear anisotropy strongly influence the formations, as well as the dynamics of the lattice solitons. Particularly, the isotropy-pattern solitons (IPSs) are found when these combined effects reach a balance. Motion, collision, and rotation of the IPSs are also studied in detail by means of systematic simulations. We further find that these IPSs can move freely in the 2D anisotropic discrete system, hence giving rise to an anisotropic effective mass. Four types of collisions between the IPSs are identified. By rotating an external magnetic field up to a critical angular velocity, the IPSs can still remain localized and play as a breather. Finally, the influences from the combined effects between the linear and the nonlocal nonlinear anisotropy with consideration of the contact and/or local nonlinearity are discussed too.

  3. Kaon and D meson masses with N_f = 2+1+1 twisted mass lattice QCD

    CERN Document Server

    Baron, Remi; Carbonell, Jaume; Drach, Vincent; Farchioni, Federico; Herdoiza, Gregorio; Jansen, Karl; Michael, Chris; Montvay, Istvan; Pallante, Elisabetta; Reker, Siebren; Urbach, Carsten; Wagner, Marc; Wenger, Urs

    2010-01-01

    We discuss the computation of the kaon and D meson masses in the N_f = 2+1+1 twisted mass lattice QCD setup, where explicit heavy flavor and parity breaking occurs at finite lattice spacing. We present three methods suitable in this context and verify their consistency.

  4. Large artificial anisotropic growth rate in on-lattice simulation of obliquely deposited nanostructures

    Science.gov (United States)

    Tanto, B.; Doiron, C. F.; Lu, T.-M.

    2011-01-01

    On-lattice particle simulation is one of the most common types of Monte Carlo simulations used in studying the dynamics of film growth. We report the observation of a large artificial anisotropic growth rate variation owing to the fixed arrangement of particles in an on-lattice simulation of oblique angle deposition. This unexpectedly large anisotropy is not reported in previous literatures and substantially affects the simulation outcomes such as column angle and porosity, two of the most essential quantities in obliquely deposited nanostructures. The result of our finding is of interest to all on-lattice simulations in obliquely deposited films or nanostructures.

  5. Lattice study on QCD-like theory with exact center symmetry

    CERN Document Server

    Iritani, Takumi; Misumi, Tatsuhiro

    2015-01-01

    We investigate QCD-like theory with exact center symmetry, with emphasis on the finite-temperature phase transition concerning center and chiral symmetries. On the lattice, we formulate center symmetric $SU(3)$ gauge theory with three fundamental Wilson quarks by twisting quark boundary conditions in a compact direction ($Z_3$-QCD model). We calculate the expectation value of Polyakov loop and the chiral condensate as a function of temperature on 16^3 x 4 and 20^3 x 4 lattices along the line of constant physics realizing $m_{PS}/m_{V}=0.70$. We find out the first-order center phase transition, where the hysteresis of the magnitude of Polyakov loop exists depending on thermalization processes. We show that chiral condensate decreases around the critical temperature in a similar way to that of the standard three-flavor QCD, as it has the hysteresis in the same range as that of Polyakov loop. We also show that the flavor symmetry breaking due to the twisted boundary condition gets qualitatively manifest in the h...

  6. Better than $1\\/Mflops$ sustained a scalable PC-based parallel computer for lattice QCD

    CERN Document Server

    Fodor, Z; Papp, G

    2003-01-01

    We study the feasibility of a PC-based parallel computer for medium to large scale lattice QCD simulations. Our cluster built at the E\\"otv\\"os Univ., Inst. Theor. Phys. consists of 137 Intel P4-1.7GHz 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^...

  7. B-meson decay constants: a more complete picture from full lattice QCD

    CERN Document Server

    Colquhoun, B; Dowdall, R J; Kettle, J; Koponen, J; Lepage, G P; Lytle, A T

    2015-01-01

    We extend the picture of $B$-meson decay constants obtained in lattice QCD beyond those of the $B$, $B_s$ and $B_c$ to give the first full lattice QCD results for the $B^*$, $B^*_s$ and $B^*_c$. We use improved NonRelativistic QCD for the valence $b$ quark and the Highly Improved Staggered Quark (HISQ) action for the lighter quarks on gluon field configurations that include the effect of $u/d$, $s$ and $c$ quarks in the sea with $u/d$ quark masses going down to physical values. For the ratio of vector to pseudoscalar decay constants, we find $f_{B^*}/f_B$ = 0.941(26), $f_{B^*_s}/f_{B_s}$ = 0.953(23) (both $2\\sigma$ less than 1.0) and $f_{B^*_c}/f_{B_c}$ = 0.988(27). Taking correlated uncertainties into account we see clear indications that the ratio increases as the mass of the lighter quark increases. We compare our results to those using the HISQ formalism for all quarks and find good agreement both on decay constant values when the heaviest quark is a $b$ and on the dependence on the mass of the heaviest q...

  8. 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.)

  9. Perfect Abelian dominance of confinement in quark-antiquark potential in SU(3) lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Suganuma, Hideo [Department of Physics, Kyoto University, Kitashirakawaoiwake, Sakyo, Kyoto 606-8502 (Japan); Sakumichi, Naoyuki [Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)

    2016-01-22

    In the context of the dual superconductor picture for the confinement mechanism, we study maximally Abelian (MA) projection of quark confinement in SU(3) quenched lattice QCD with 32{sup 4} at β=6.4 (i.e., a ≃ 0.058 fm). We investigate the static quark-antiquark potential V(r), its Abelian part V{sub Abel}(r) and its off-diagonal part V{sub off}(r), respectively, from the on-axis lattice data. As a remarkable fact, we find almost perfect Abelian dominance for quark confinement, i.e., σ{sub Abel} ≃ σ for the string tension, on the fine and large-volume lattice. We find also a nontrivial summation relation of V (r) ≃ V{sub Abel}(r)+V{sub off}(r)

  10. 2+1 flavor lattice QCD with Luscher's Domain-Decomposed HMC algorithm

    Science.gov (United States)

    Kuramashi, Yoshinobu

    2006-12-01

    We report on a study of 2+1 flavor lattice QCD with the O(a)-improved Wilson quarks on a 163 × 32 lattice at the lattice spacing 1/a ≈ 2GeV employing Lüscher's domain-decomposed HMC(LDDHMC) algorithm. This is dedicated to a preliminary study for the PACS-CS project which plans to complete the Wilson-clover N f = 2 + 1 program lowering the up-down quark masses close to the physical values as much as possible. We focus on three issues: (i) how light quark masses we can reach with LDDHMC, (ii) efficiency of the algorithm compared with the conventional HMC, (iii) parameter choice for the production runs on PACS-CS.

  11. 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.

  12. The hadronic vacuum polarization contribution to $a_{\\mu}$ from full lattice QCD

    CERN Document Server

    Chakraborty, Bipasha; de Oliviera, P G; Koponen, J; Lepage, G P

    2016-01-01

    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 $666(6)(12)$, 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$\\sigma$.

  13. Landau gauge gluon and ghost propagators from two-flavor lattice QCD at T > 0

    CERN Document Server

    Aouane, R; Muller-Preussker, M; Ilgenfritz, E -M; Sternbeck, A

    2013-01-01

    In this contribution we extend our unquenched computation of the Landau gauge gluon and ghost propagators in lattice QCD at non-zero temperature. The study was aimed at providing input for investigations employing continuum functional methods. We show data which correspond to pion mass values between 300 and 500 MeV and are obtained for a lattice size 32**3 x 12. The longitudinal and transversal components of the gluon propagator turn out to change smoothly through the crossover region, while the ghost propagator exhibits only a very weak temperature dependence. For a pion mass of around 400 MeV and the intermediate temperature value of approx. 240 MeV we compare our results with additional data obtained on a lattice with smaller Euclidean time extent N_t = 8, 10 and find a reasonable scaling behavior.

  14. 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.

  15. Hadronic matrix elements of neutral-meson mixing through lattice QCD

    CERN Document Server

    Chang, C C

    2015-01-01

    Neutral-meson mixing is loop suppressed in the Standard Model, leading to the possibility of enhanced sensitivity to new physics. The uncertainty in Standard Model predictions for $B$-meson oscillation frequencies is dominated by theoretical uncertainties within the short-distance $B$-meson hadronic matrix elements, motivating the need for improved precision. In $D$-meson mixing, the Standard Model short-distance contributions are further suppressed by the GIM mechanism allowing for the possibility of large new physics enhancements. A first-principle determination of the $D$-meson short-distance hadronic matrix elements will allow for model-discrimination between the new physics theories. I review recently published and ongoing lattice calculations of hadronic matrix elements in $B$ and $D$-meson mixing with emphasis on the Fermilab lattice and MILC collaboration effort on the determination of the $B$ and $D$-meson mixing hadronic matrix elements using the methods of lattice QCD.

  16. 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.

  17. I=2 ππ scattering from fully-dynamical mixed-action lattice QCD

    Science.gov (United States)

    Beane, Silas R.; Bedaque, Paulo F.; Orginos, Kostas; Savage, Martin J.

    2006-03-01

    We compute the I=2 ππ scattering length at pion masses of mπ˜294, 348, and 484 MeV in fully-dynamical lattice QCD using Lüscher’s finite-volume method. The calculation is performed with domain-wall valence-quark propagators on asqtad-improved MILC configurations with staggered sea quarks at a single lattice spacing, b˜0.125fm. Chiral perturbation theory is used to perform the extrapolation of the scattering length from lattice quark masses down to the physical value, and we find mπa2=-0.0426±0.0006±0.0003±0.0018, in good agreement with experiment. The I=2 ππ scattering phase shift is calculated to be δ=-43±10±5° at |p|˜544MeV for mπ˜484MeV.

  18. Potential description of the charmonium from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Kawanai, Taichi [Jülich Supercomputing Center, Jülich D-52425 (Germany); Sasaki, Shoichi [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)

    2016-01-22

    We present spin-independent and spin-spin interquark potentials for charmonium states, that are calculated using a relativistic heavy quark action for charm quarks on the PACS-CS gauge configurations generated with the Iwasaki gauge action and 2+1 flavors of Wilson clover quark. The interquark potential with finite quark masses is defined through the equal-time Bethe-Salpeter amplitude. The light and strange quark masses are close to the physical point where the pion mass corresponds to M{sub π} ≈ 156(7) MeV, and charm quark mass is tuned to reproduce the experimental values of η{sub c} and J/ψ states. Our simulations are performed with a lattice cutoff of a{sup −1} ≈ 2.2 GeV and a spatial volume of (3 fm){sup 3}. We solve the nonrelativistic Schrödinger equation with resulting charmonium potentials as theoretical inputs. The resultant charmonium spectrum below the open charm threshold shows a fairly good agreement with experimental data of well-established charmonium states.

  19. Scattering from finite size methods in lattice QCD

    CERN Document Server

    Feng, Xu; Renner, Dru B

    2009-01-01

    Using two flavors of maximally twisted mass fermions, we calculate the S-wave pion-pion scattering length in the isospin I=2 channel and the P-wave pion-pion scattering phase in the isospin I=1 channel. In the former channel, the lattice calculations are performed at pion masses ranging from 270 MeV to 485 MeV. We use chiral perturbation theory at next-to-leading order to extrapolate our results. At the physical pion mass, we find m_pi a_pipi(I=2)=-0.04385(28)(38) for the scattering length. In the latter channel, the calculation is currently performed at a single pion mass of 391 MeV. Making use of finite size methods, we evaluate the scattering phase in both the center of mass frame and the moving frame. The effective range formula is employed to fit our results, from which the rho resonance mass and decay width are evaluated.

  20. Spin Relaxation in Kondo Lattice Systems with Anisotropic Kondo Interaction

    Science.gov (United States)

    Belov, S. I.; Kutuzov, A. S.

    2016-12-01

    We study the influence of the Kondo effect on the spin relaxation in systems with anisotropic Kondo interaction at temperatures both high and low as compared with the static magnetic field. In the absence of the Kondo effect, the electron spin resonance linewidth is not narrowed in the whole temperature range due to the high anisotropy of the Kondo interaction. The Kondo effect leads to the universal energy scale, which regulates the temperature and magnetic field dependence of different kinetic coefficients and results in a mutual cancelation of their singular parts in a collective spin mode.

  1. Finite Temperature Lattice QCD - Baryons in the Quark-Gluon Plasma

    CERN Document Server

    Aarts, Gert; De Boni, Davide; Hands, Simon; Jäger, Benjamin; Praki, Chrisanthi; Skullerud, Jon-Ivar

    2016-01-01

    Baryonic correlation functions provide an ideal tool to study parity doubling and chiral symmetry using lattice simulations. We present a study using $2+1$ flavors of anisotropic Wilson clover fermions on the FASTSUM ensembles and find clear evidence that parity doubling emerges in the quark-gluon plasma. This result is confirmed on the level of spectral functions, which are obtained using a MEM reconstruction. We further highlight the importance of Gaussian smearing in this study.

  2. On the Determination of Elastic and Inelastic Nuclear Observables from Lattice QCD

    CERN Document Server

    Briceno, Raul A

    2013-01-01

    One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of the strong interaction, Quantum Chromodynamics (QCD). Currently, lattice QCD (LQCD) provides the only reliable option for performing calculations of low-energy hadronic observables. LQCD calculations are necessarily performed in a finite Euclidean spacetime. As a result, it is necessary to construct formalism that maps the finite-volume observables determined via LQCD to the infinite-volume quantities of interest. This methodology is commonly referred to as the Luscher method, as it was Martin Luscher who first developed such formalism for scalar bosons with zero total momentum below inelastic thresholds. In this work, we review recent progress on the generalization of this formalism. We present a detailed derivation of the extension of Luscher's seminal work for multi-channel two-body scalar systems, two-nucleon non-relativistic systems, and three-body non-relativist...

  3. Investigation of the $U_A(1)$ in high temperature QCD on the lattice

    CERN Document Server

    Sharma, Sayantan; Karsch, Frithjof; Laermann, Edwin; Mukherjee, Swagato

    2013-01-01

    In this project we study the effect of the $U_A(1)$ anomaly for (2+1)-flavour QCD at high temperature. We apply the overlap operator as a tool to probe the topological properties of gauge field configurations which have been generated within the Highly Improved Staggered Quark (HISQ) discretization scheme on lattices of size $32^3\\times 8$ with $m_l/m_s=1/20$, commonly used for the study of QCD thermodynamics. Although we have at present, only results for one value of the quark masses and thus cannot monitor the change of the eigenvalue distributions with the light quark mass, the distribution of the low-lying eigenvalues of the overlap operator suggests that the $U_A(1)$ is not restored effectively even at 1.5 times the pseudo critical temperature. The corresponding low-lying eigenmodes show localization properties.

  4. A study of the radiative transition $\\pi \\pi \\to \\pi \\gamma^{*}$ with lattice QCD

    CERN Document Server

    Leskovec, Luka; Koutsou, Giannis; Meinel, Stefan; Negele, John W; Paul, Srijit; Petschlies, Marcus; Pochinsky, Andrew; Rendon, Gumaro; Syritsyn, Sergey

    2016-01-01

    Lattice QCD calculations of radiative transitions between hadrons have in the past been limited to processes of hadrons stable under the strong interaction. Recently developed methods for $1\\to2$ transition matrix elements in a finite volume now enable the determination of radiative decay rates of strongly unstable particles. Our lattice QCD study focuses on the process $\\pi \\pi \\to \\pi \\gamma^{*}$, where the $\\rho$ meson is present as an enhancement in the cross-section. We use $2+1$ flavors of clover fermions at a pion mass of approximately $320$ MeV and a lattice size of approximately $3.6$ fm. The required $2$-point and $3$-point correlation functions are constructed from a set of forward, sequential and stochastic light quark propagators. In addition to determining the $\\rho$ meson resonance parameters via the L\\"uscher method, the scattering phase shift is used in conjunction with the $1\\to2$ transition matrix element formalism of Brice\\~no, Hansen and Walker-Loud to compute the $\\pi\\pi\\to\\pi\\gamma^{*}$...

  5. Lattice QCD with Nf=2+1+1 domain-wall quarks

    Directory of Open Access Journals (Sweden)

    Yu-Chih Chen

    2017-04-01

    Full Text Available We perform hybrid Monte Carlo simulation of (2+1+1-flavors lattice QCD with the optimal domain-wall fermion (which has the effective 4D Dirac operator exactly equal to the Zolotarev optimal rational approximation of the overlap Dirac operator. The gauge ensemble is generated on the 323×64 lattice with the extent Ns=16 in the fifth dimension, and with the plaquette gauge action at β=6/g2=6.20. The lattice spacing (a≃0.063 fm is determined by the Wilson flow, using the value t0=0.1416(8 fm obtained by the MILC Collaboration for the (2+1+1-flavors QCD. The masses of s and c quarks are fixed by the masses of the vector mesons ϕ(1020 and J/ψ(3097 respectively; while the mass of the u/d quarks is heavier than their physical values, with the unitary pion mass Mπ≃280 MeV (and MπL≃3. We compute the point-to-point quark propagators, and measure the time-correlation functions of meson and baryon interpolators. Our results of the mass spectra of the lowest-lying hadrons containing s and c quarks are in good agreement with the high energy experimental values, together with the predictions of the charmed baryons which have not been observed in experiments.

  6. Lattice QCD with Nf = 2 + 1 + 1 domain-wall quarks

    Science.gov (United States)

    Chen, Yu-Chih; Chiu, Ting-Wai

    2017-04-01

    We perform hybrid Monte Carlo simulation of (2 + 1 + 1)-flavors lattice QCD with the optimal domain-wall fermion (which has the effective 4D Dirac operator exactly equal to the Zolotarev optimal rational approximation of the overlap Dirac operator). The gauge ensemble is generated on the 323 × 64 lattice with the extent Ns = 16 in the fifth dimension, and with the plaquette gauge action at β = 6 /g2 = 6.20. The lattice spacing (a ≃ 0.063 fm) is determined by the Wilson flow, using the value √{t0} = 0.1416 (8) fm obtained by the MILC Collaboration for the (2 + 1 + 1)-flavors QCD. The masses of s and c quarks are fixed by the masses of the vector mesons ϕ (1020) and J / ψ (3097) respectively; while the mass of the u / d quarks is heavier than their physical values, with the unitary pion mass Mπ ≃ 280 MeV (and Mπ L ≃ 3). We compute the point-to-point quark propagators, and measure the time-correlation functions of meson and baryon interpolators. Our results of the mass spectra of the lowest-lying hadrons containing s and c quarks are in good agreement with the high energy experimental values, together with the predictions of the charmed baryons which have not been observed in experiments.

  7. $B\\to Kl^+l^-$ decay form factors from three-flavor lattice QCD

    CERN Document Server

    Bailey, Jon A; Bernard, C; Bouchard, C M; DeTar, C; Du, Daping; El-Khadra, A X; Foley, J; Freeland, E D; Gámiz, E; Gottlieb, Steven; Heller, U M; Jain, R D; Komijani, J; Kronfeld, A S; Laiho, J; Levkova, L; Liu, Yuzhi; Mackenzie, P B; Meurice, Y; Neil, E T; Qiu, Si-Wei; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, Ran

    2015-01-01

    We compute the form factors for the $B \\to Kl^+l^-$ semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy $b$ quark. We present results for the form factors $f_+(q^2)$, $f_0(q^2)$, and $f_T(q^2)$, where $q^2$ is the momentum transfer, together with a comprehensive examination of systematic errors. Lattice QCD determines the form factors for a limited range of $q^2$, and we use the model-independent $z$ expansion to cover the whole kinematically allowed range. We present our final form-factor results as coefficients of the $z$ expansion and the correlations between them, where the errors on the coefficients include statistical and all sys...

  8. The chiral transition and U(1)_A symmetry restoration from lattice QCD using Domain Wall Fermions

    CERN Document Server

    Bazavov, A; Buchoff, Michael I; Cheng, Michael; Christ, N H; Ding, H -T; Gupta, Rajan; Hegde, Prasad; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; Mukherjee, Swagato; Petreczky, P; Soltz, R A; Vranas, P M; Yin, Hantao

    2012-01-01

    We present results on both the restoration of the spontaneously broken chiral symmetry and the effective restoration of the anomalously broken U(1)_A symmetry in finite temperature QCD at zero chemical potential using lattice QCD. We employ domain wall fermions on lattices with fixed temporal extent N_\\tau = 8 and spatial extent N_\\sigma = 16 in a temperature range of T = 139 - 195 MeV, corresponding to lattice spacings of a \\approx 0.12 - 0.18 fm. In these calculations, we include two degenerate light quarks and a strange quark at fixed pion mass m_\\pi = 200 MeV. The strange quark mass is set near its physical value. We also present results from a second set of finite temperature gauge configurations at the same volume and temporal extent with slightly heavier pion mass. To study chiral symmetry restoration, we calculate the chiral condensate, the disconnected chiral susceptibility, and susceptibilities in several meson channels of different quantum numbers. To study U(1)_A restoration, we calculate spatial ...

  9. Mirage in Temporal Correlation functions for Baryon-Baryon Interactions in Lattice QCD

    CERN Document Server

    Iritani, Takumi; Aoki, Sinya; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

    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 the 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 ($\\Xi\\Xi$ and $NN$), and three and four baryons ($^3{\\rm He}$ and $^4{\\rm He})$ as well, employing (2+1)-flavor lattice QCD at $m_{\\pi}=0.51$ GeV on four lattice volumes with $L=$ 2.9, 3.6, 4.3 and 5.8 fm. Caution is given for drawing conclusion on the bound $NN$, $3N$ and $4N$ systems only based on the temporal correlation functions.

  10. Melting of the Abrikosov flux lattice in anisotropic superconductors

    Science.gov (United States)

    Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

    1992-01-01

    It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

  11. The static-light meson spectrum from twisted mass lattice QCD

    CERN Document Server

    Jansen, Karl; Shindler, Andrea; Wagner, Marc

    2008-01-01

    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 < m_PS < 600 MeV and we present results for angular momentum j = 1/2, j = 3/2 and j = 5/2 and for parity P = + and P = -. We extrapolate our results to physical quark masses and make predictions regarding the spectrum of B and B_s mesons.

  12. Axial-Current Matrix Elements in Light Nuclei from Lattice QCD

    CERN Document Server

    Savage, Martin J; Tiburzi, Brian C; Wagman, Michael L; Winter, Frank; Beane, Silas R; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas

    2016-01-01

    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.

  13. Precise Determination of the I = 2 Scattering Length from Mixed-Action Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Silas Beane; Paulo Bedaque; Thomas Luu; Konstantinos Orginos; Assumpta Parreno; Martin Savage; Aaron Torok; Andre Walker-Loud

    2008-01-01

    The I=2 pipi scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations (with fourth-rooted staggered sea quarks) at four light-quark masses. Two- and three-flavor mixed-action chiral perturbation theory at next-to-leading order is used to perform the chiral and continuum extrapolations. At the physical charged pion mass, we find m_pi a_pipi(I=2) = -0.04330 +- 0.00042, where the error bar combines the statistical and systematic uncertainties in quadrature.

  14. Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD

    CERN Document Server

    Meyer, Aaron S; Kronfeld, Andreas S; Li, Ruizi; Simone, James N

    2016-01-01

    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.

  15. Ωcγ→Ωc⁎ transition in lattice QCD

    Directory of Open Access Journals (Sweden)

    H. Bahtiyar

    2015-07-01

    Full Text Available We study the electromagnetic Ωcγ→Ωc⁎ transition in 2+1 flavor lattice QCD, which gives access to the dominant decay mode of Ωc⁎ baryon. The magnetic dipole and the electric quadrupole transition form factors are computed. The magnetic dipole form factor is found to be mainly determined by the strange quark and the electric quadrupole form factor to be negligibly small, in consistency with the quark model. We also evaluate the helicity amplitudes and the decay rate.

  16. Nucleon Scalar and Tensor Charges from Lattice QCD with Light Wilson Quarks

    CERN Document Server

    Green, J R; Pochinsky, A V; Syritsyn, S N; Engelhardt, M; Krieg, S

    2012-01-01

    We present 2+1 flavor Lattice QCD calculations of the nucleon scalar and tensor charges. Using the BMW clover-improved Wilson action with pion masses between 150 and 350 MeV and three source-sink separations between 0.9 and 1.4 fm, we achieve good control over excited-state contamination and extrapolation to the physical pion mass. As a consistency check, we also present results from calculations using unitary domain wall fermions with pion masses between 300 and 400 MeV, and using domain wall valence quarks and staggered sea quarks with pion masses between 300 and 600 MeV.

  17. 2+1 flavor QCD simulation on a $96^4$ lattice

    CERN Document Server

    Ishikawa, K -I; Kuramashi, Y; Nakamura, Y; Namekawa, Y; Taniguchi, Y; Ukita, N; Yamazaki, T; Yoshie, T

    2015-01-01

    We generate $2+1$ flavor QCD configurations near the physical point on a $96^4$ lattice employing the 6-APE stout smeared Wilson clover action with a nonperturbative $c_{\\rm SW}$ and the Iwasaki gauge action at $\\beta=1.82$. The physical point is estimated based on the chiral perturbation theory using several data points generated by the reweighting technique from the simulation point, wherer $m_\\pi$,$m_K$ and $m_\\Omega$ are used as physical inputs. The physics results include the quark masses, the hadron spectrum, the pseudoscalar meson decay constants and nucleon sigma terms, using the nonperturbative renormalization factors evaluated with the Schrodinger functional method.

  18. Precise Determination of the I=2 pipi Scattering Length from Mixed-Action Lattice QCD

    CERN Document Server

    Beane, Silas R; Orginos, Kostas; Parreno, Assumpta; Savage, Martin J; Torok, Aaron; Walker-Loud, Andre

    2007-01-01

    The I=2 pipi scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations (with fourth-rooted staggered sea quarks) at four light-quark masses. Two- and three-flavor mixed-action chiral perturbation theory at next-to-leading order is used to perform the chiral and continuum extrapolations. At the physical charged pion mass, we find m_pi a_pipi(I=2) = -0.04330 +- 0.00042, where the error bar combines the statistical and systematic uncertainties in quadrature.

  19. Spectral properties of quarks above $\\T_{c}$ in quenched lattice QCD

    CERN Document Server

    Karsch, Frithjof

    2007-01-01

    We analyze the quark spectral function above the critical temperature for deconfinement in quenched lattice QCD using clover improved Wilson fermions in Landau gauge. We show that the temporal quark correlator is well reproduced by a two-pole approximation for the spectral function and analyze the bare quark mass dependence of both poles as well as their residues. In the chiral limit we find that the quark spectral function has two collective modes which correspond to the normal and plasmino excitations. At large values of the bare quark mass the spectral function is dominated by a single pole.

  20. The strong running coupling at $\\tau$ and $Z_0$ mass scales from lattice QCD

    CERN Document Server

    Blossier, B; Brinet, M; De Soto, F; Du, X; Morenas, V; Pène, O; Petrov, K; Rodríguez-Quintero, J

    2012-01-01

    This letter reports on the first computation, from data obtained in lattice QCD with $u,d,s$ and $c$ quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the MOM Taylor scheme. We provide with estimates of $\\alpha_{\\bar{\\rm MS}}(m_\\tau^2)$ and $\\alpha_{\\bar{\\rm MS}}(m_Z^2)$ (for which the inclusion of the dynamical charm quark makes the running much safer) in very good agreement with experimental results.

  1. Light hadrons from lattice QCD with light (u,d), strange and charm dynamical quarks

    CERN Document Server

    Baron, Remi; Carbonell, Jaume; Deuzeman, Albert; Drach, Vincent; Farchioni, Federico; Gimenez, Vicent; Herdoiza, Gregorio; Jansen, Karl; McNeile, Craig; Michael, Chris; Montvay, Istvan; Palao, David; Pallante, Elisabetta; Pene, Olivier; Reker, Siebren; Urbach, Carsten; Wagner, Marc; Wenger, Urs

    2010-01-01

    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 < m_PS < 510 MeV and determine the low energy parameters f_0, l_3 and l_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.

  2. 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.

  3. Extrapolation of lattice QCD results beyond the power-counting regime

    CERN Document Server

    Leinweber, D B; Young, R D

    2005-01-01

    Resummation of the chiral expansion is necessary to make accurate contact with current lattice simulation results of full QCD. Resummation techniques including relativistic formulations of chiral effective field theory and finite-range regularization (FRR) techniques are reviewed, with an emphasis on using lattice simulation results to constrain the parameters of the chiral expansion. We illustrate how the chiral extrapolation problem has been solved and use FRR techniques to identify the power-counting regime (PCR) of chiral perturbation theory. To fourth-order in the expansion at the 1% tolerance level, we find $0 \\le m_\\pi \\le 0.18$ GeV for the PCR, extending only a small distance beyond the physical pion mass.

  4. Hadron spectrum in quenched lattice QCD and distribution of zero modes

    Energy Technology Data Exchange (ETDEWEB)

    Iwasaki, Yoichi (Tsukuba Univ., Sakura, Ibaraki (Japan). Inst. of Physics)

    1989-06-01

    I report the results of the calculation of the hadron spectrum with the standard one-plaquette gauge action on a 16{sup 3}x48 lattice at beta=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.).

  5. Heavy Quark Thermalization in Classical Lattice Gauge Theory Lessons for Strongly-Coupled QCD

    CERN Document Server

    Laine, Mikko; Philipsen, Owe; Tassler, Marcus

    2009-01-01

    Thermalization of a heavy quark near rest is controlled by the correlator of two electric fields along a temporal Wilson line. We address this correlator within real-time, classical lattice Yang-Mills theory, and elaborate on the analogies that exist with the dynamics of hot QCD. In the weak-coupling limit, it can be shown analytically that the dynamics on the two sides are closely related to each other. For intermediate couplings, we carry out non-perturbative simulations within the classical theory, showing that the leading term in the weak-coupling expansion significantly underestimates the heavy quark thermalization rate. Our analytic and numerical results also yield a general understanding concerning the overall shape of the spectral function corresponding to the electric field correlator, which may be helpful in subsequent efforts to reconstruct it from Euclidean lattice Monte Carlo simulations.

  6. 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.

  7. Solving Lattice QCD systems of equations using mixed precision solvers on GPUs

    CERN Document Server

    Clark, M A; Barros, K; Brower, R C; Rebbi, C

    2009-01-01

    Modern graphics hardware is designed for highly parallel numerical tasks and promises significant cost and performance benefits for many scientific applications. One such application is lattice quantum chromodyamics (lattice QCD), where the main computational challenge is to efficiently solve the discretized Dirac equation in the presence of an SU(3) gauge field. Using NVIDIA's CUDA platform we have implemented a Wilson-Dirac sparse matrix-vector product that performs at up to 36 Gflops, 135 Gflops and 205 Gflops for double, single and half precision respectively on NVIDIA's GeForce GTX 280 GPU. We have developed a new mixed precision approach for Krylov solvers using reliable updates which allows for full double precision accuracy while using only single or half precision arithmetic for the bulk of the computation. The resulting BiCGstab and CG solvers run in excess of 100 Gflops and, in terms of iterations until convergence, perform better than the usual defect-correction approach for mixed precision.

  8. High-Performance I/O: HDF5 for Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Thorsten; Pochinsky, Andrew; Sarje, Abhinav; Syritsyn, Sergey; Walker-Loud, Andre

    2015-01-01

    Practitioners of lattice QCD/QFT have been some of the primary pioneer users of the state-of-the-art high-performance-computing systems, and contribute towards the stress tests of such new machines as soon as they become available. As with all aspects of high-performance-computing, I/O is becoming an increasingly specialized component of these systems. In order to take advantage of the latest available high-performance I/O infrastructure, to ensure reliability and backwards compatibility of data files, and to help unify the data structures used in lattice codes, we have incorporated parallel HDF5 I/O into the SciDAC supported USQCD software stack. Here we present the design and implementation of this I/O framework. Our HDF5 implementation outperforms optimized QIO at the 10-20% level and leaves room for further improvement by utilizing appropriate dataset chunking.

  9. Direct Evaluation of the Quark Content of Nucleons from Lattice QCD at the Physical Point.

    Science.gov (United States)

    Abdel-Rehim, A; Alexandrou, C; Constantinou, M; Hadjiyiannakou, K; Jansen, K; Kallidonis, Ch; Koutsou, G; Avilés-Casco, A Vaquero

    2016-06-24

    We evaluate the light, strange, and charm scalar content of the nucleon using one lattice QCD ensemble generated with two degenerate light quarks with mass fixed to their physical value. We use improved techniques to evaluate the disconnected quark loops to sufficient accuracy to determine the strange and charm nucleon σ terms in addition to the light quark content σ_{πN}. We find σ_{πN}=37.2(2.6)(4.7/2.9)  MeV, σ_{s}=41.1(8.2)(7.8/5.8)  MeV, and σ_{c}=79(21)(12/8)  MeV, where the first error is statistical and the second is the systematic error due to the determination of the lattice spacing, the assessment of finite volume, and residual excited state effects.

  10. I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD

    CERN Document Server

    Beane, S R; Orginos, K; Savage, M J; Beane, Silas R.; Bedaque, Paulo F.; Orginos, Kostas; Savage, Martin J.

    2006-01-01

    We compute the I=2 pi-pi scattering length at pion masses of m_pi= 294, 348 and 484 MeV in fully-dynamical lattice QCD using Luscher's finite-volume method. The calculation is performed with domain-wall valence-quark propagators on asqtad-improved MILC configurations with staggered sea quarks. Chiral perturbation theory is used to perform the extrapolation of the scattering length from lattice quark masses down to the physical value, and we find m_pi a_2 = -0.0426 +- 0.0006 +- 0.0003 +- 0.0018, in good agreement with experiment. The I=2 pi-pi scattering phase shift is calculated to be delta ~ -43 +- 10 +- 5 degrees at |p| ~ 544 MeV for m_pi ~ 484 MeV.

  11. 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 Nf = 2+1 lattice QCD. We use a large set of the MIMD Lattice Computation Collaboration's gauge configurations with a2 tadpole-improved staggered sea quarks and tadpole-improved Lüscher-Weisz gluons. We use the a2 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.

  12. Non-perturbative test of the Witten-Veneziano formula from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Garcia-Ramos, Elena [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Ottnad, Konstantin; Urbach, Carsten [Bonn Univ. (Germany). Institut fuer Strahlen- und Kernphysik; Bonn Univ. (Germany). Bethe Center for Theoretical Physics; Collaboration: The ETM collaboration

    2015-10-15

    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{sub 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.

  13. B-meson decay constants from 2+1-flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

    CERN Document Server

    Christ, Norman H; Izubuchi, Taku; Kawanai, Taichi; Lehner, Christoph; Soni, Amarjit; Van de Water, Ruth S; Witzel, Oliver

    2014-01-01

    We calculate the B-meson decay constants f_B, f_Bs, and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b-quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ~ 0.11, 0.086 fm with unitary pion masses as light as M_pi ~ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b-quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also impr...

  14. Axial, scalar, and tensor charges of the nucleon from 2 +1 +1 -flavor Lattice QCD

    Science.gov (United States)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Cohen, Saul D.; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram; Precision Neutron Decay Matrix Elements Pndme Collaboration

    2016-09-01

    We present results for the isovector axial, scalar, and tensor charges gAu -d , gSu -d, and gTu -d of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear β -decays, and the flavor-diagonal tensor charges gTu, gTd, and gTs are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks action with 2 +1 +1 dynamical flavors. These ensembles span three lattice spacings a ≈0.06 ,0.09 , and 0.12 fm and light-quark masses corresponding to the pion masses Mπ≈135 ,225 , and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the MS ¯ scheme at 2 GeV, of the isovector charges are gAu -d=1.195 (33 )(20 ) , gSu -d=0.97 (12 )(6 ), and gTu -d=0.987 (51 )(20 ) . The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for gSu -d with the difference of light quarks masses (md-mu)QCD=2.67 (35 ) MeV given by the Flavor Lattice Average Group, we obtain (MN-MP)QCD=2.59 (49 ) MeV . Estimates of the connected part of the flavor-diagonal tensor charges of the proton are gTu=0.792 (42 ) and gTd=-0.194 (14 ). Combining our new estimates with precision low-energy experiments, we present updated constraints on novel scalar and tensor interactions, ɛS ,T, at the TeV scale.

  15. Complex spectrum of finite-density lattice QCD with static quarks at strong coupling

    CERN Document Server

    Nishimura, Hiromichi; Pangeni, Kamal

    2015-01-01

    We calculate the spectrum of transfer matrix eigenvalues associated with Polyakov loops in finite-density lattice QCD with static quarks. These eigenvalues determine the spatial behavior of Polyakov loop correlations functions. Our results are valid for all values of the gauge coupling in $1+1$ dimensions, and valid in the strong-coupling region for any number of dimensions. When the quark chemical potential $\\mu$ is nonzero, the spatial transfer matrix $T$ is non-Hermitian. The appearance of complex eigenvalues in $T$ is a manifestation of the sign problem in finite-density QCD. The invariance of finite-density QCD under the combined action of charge conjugation $\\mathcal{C}$ and complex conjugation $\\mathcal{K}$ implies that the eigenvalues of $T$ are either real or part of a complex pair. Calculation of the spectrum confirms the existence of complex pairs in much of the temperature-chemical potential plane. Many features of the spectrum for static quarks are determined by a particle-hole symmetry. For $\\mu...

  16. K-->pipi amplitudes from lattice QCD with a light charm quark.

    Science.gov (United States)

    Giusti, L; Hernández, P; Laine, M; Pena, C; Wennekers, J; Wittig, H

    2007-02-23

    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. They 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 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. The use of fermions with an exact chiral symmetry is an essential ingredient in our computation.

  17. Another mean field treatment in the strong coupling limit of lattice QCD

    CERN Document Server

    Ohnishi, Akira; Nakano, Takashi Z

    2010-01-01

    We discuss the QCD phase diagram in the strong coupling limit of lattice QCD by using a new type of mean field coming from the next-to-leading order of the large dimensional expansion. The QCD phase diagram in the strong coupling limit recently obtained by using the monomer-dimer-polymer (MDP) algorithm has some differences in the phase boundary shape from that in the mean field results. As one of the origin to explain the difference, we consider another type of auxiliary field, which corresponds to the point-splitting mesonic composite. Fermion determinant with this mean field under the anti-periodic boundary condition gives rise to a term which interpolates the effective potentials in the previously proposed zero and finite temperature mean field treatments. While the shift of the transition temperature at zero chemical potential is in the desirable direction and the phase boundary shape is improved, we find that the effects are too large to be compatible with the MDP simulation results.

  18. Lattice QCD and physics beyond the Standar Model: an experimentalist perspective

    Science.gov (United States)

    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.

  19. Majorana modes and topological superfluids for ultracold fermionic atoms in anisotropic square optical lattices

    Science.gov (United States)

    Wu, Ya-Jie; Li, Ning; Kou, Su-Peng

    2016-12-01

    Motivated by the recent experimental realization of two-dimensional spin-orbit coupling through optical Raman lattice scheme, we study attractive interacting ultracold gases with spin-orbit interaction in anisotropic square optical lattices, and find that rich s-wave topological superfluids can be realized, including Z2 topological superfluids beyond the characterization of "tenfold way" in addition to chiral topological superfluids. The topological defects-superfluid vortex and edge dislocations-may host Majorana modes in some topological superfluids, which are helpful for realizing topological quantum computation and Majorana fermionic quantum computation. In addition, we also discuss the Berezinsky-Kosterlitz-Thouless phase transitions for different topological superfluids.

  20. Quenched Charmed Meson Spectra Using Tadpole Improved Quark Action on Anisotropic Lattices

    Institute of Scientific and Technical Information of China (English)

    LIU Liu-Ming; SU Shi-Quan; LI Xin; LIU Chuan

    2005-01-01

    @@ Charmed meson charmonium spectra are studied with improved quark actions on anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion relations for four lowest lattice momentum modes with quark mass values ranging from the strange quark to charm quark with three different values of gauge coupling β and four different values of bare speed of light v. With the bare speed of light parameter v tuned in a mass-dependent way, we study the mass spectra of D, Ds, ηc, D*, Ds* and J/ψ mesons. The results extrapolated to the continuum limit are compared with the experiment, and a qualitative agreement is found.

  1. Vortex-lattice pinning and critical current density in anisotropic high-temperature superconductors

    Science.gov (United States)

    Li, Yingxu; Li, Xiangyu; Kang, Guozheng; Gao, Yuanwen

    2016-10-01

    The anisotropy of critical current density is an impressive manifestation in the physics of high-temperature superconductors. We develop an analytical characterization of anisotropic flux-lattice pinning and critical current density in a system of random point defects. The effect of superconducting anisotropy on the pinning force and critical current density is formulated. The in-plane/out-of-plane anisotropy and microscopic characteristic lengths are incorporated in the field and angular dependence of the critical current density. This is helpful in understanding the physical essence of the scaling behavior in the experiments for critical current anisotropy. We discuss the role of strong and weak point defects in the anisotropic flux-lattice pinning. Relevance of the theory to the critical-state model is dictated as well.

  2. Semileptonic D->pi/K and B->pi/D decays in 2+1 flavor lattice QCD

    CERN Document Server

    Okamoto, M; Bernard, C; DeTar, C; Di Pierro, Massimo; El-Khadra, A X; Gottlieb, S; Gregory, E B; Heller, U M; Hetrick, J E; Kronfeld, A S; MacKenzie, P B; Menscher, D P; Nobes, M; Oktay, M B; Osborn, J; Simone, J N; Sugar, R; Toussaint, D; Trottier, H D; Gottlieb, Steven

    2005-01-01

    We present results for form factors of semileptonic decays of $D$ and $B$ mesons in 2+1 flavor lattice QCD using the MILC gauge configurations. With an improved staggered action for light quarks, we successfully reduce the systematic error from the chiral extrapolation. The results for $D$ decays are in agreement with experimental ones. The results for B decays are preliminary. Combining our results with experimental branching ratios, we then obtain the CKM matrix elements $|V_{cd}|$, $|V_{cs}|$, $|V_{cb}|$ and $|V_{ub}|$. We also check CKM unitarity, for the first time, using only lattice QCD as the theoretical input.

  3. Equation of state for nucleonic matter and its quark mass dependence from the nuclear force in lattice QCD.

    Science.gov (United States)

    Inoue, Takashi; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

    2013-09-13

    Quark mass dependence of the equation of state (EOS) for nucleonic matter is investigated, on the basis of the Brueckner-Hartree-Fock method with the nucleon-nucleon interaction extracted from lattice QCD simulations. We observe saturation of nuclear matter at the lightest available quark mass corresponding to the pseudoscalar meson mass ≃469  MeV. Mass-radius relation of the neutron stars is also studied with the EOS for neutron-star matter from the same nuclear force in lattice QCD. We observe that the EOS becomes stiffer and thus the maximum mass of neutron star increases as the quark mass decreases toward the physical point.

  4. Anisotropic Hubbard model on a triangular lattice - spin dynamics in HoMnO3

    Indian Academy of Sciences (India)

    Saptarshi Ghosh; Avinash Singh

    2008-01-01

    The recent neutron scattering data for spin-wave dispersion in HoMnO3 are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates that magnetic excitations in HoMnO3 correspond to the strong-coupling limit / > ∼ 15, with planar exchange energy = 42/ ≃ 2.5 meV and planar anisotropy ≃ 0.35 meV.

  5. Spontaneous chiral symmetry breaking in QCD:a finite-size scaling study on the lattice

    CERN Document Server

    Giusti, Leonardo; Giusti, Leonardo; Necco, Silvia

    2007-01-01

    Spontaneous chiral symmetry breaking in QCD with massless quarks at infinite volume can be seen in a finite box by studying, for instance, the dependence of the chiral condensate from the volume and the quark mass. We perform a feasibility study of this program by computing the quark condensate on the lattice in the quenched approximation of QCD at small quark masses. We carry out simulations in various topological sectors of the theory at several volumes, quark masses and lattice spacings by employing fermions with an exact chiral symmetry, and we focus on observables which are infrared stable and free from mass-dependent ultraviolet divergences. The numerical calculation is carried out with an exact variance-reduction technique, which is designed to be particularly efficient when spontaneous symmetry breaking is at work in generating a few very small low-lying eigenvalues of the Dirac operator. The finite-size scaling behaviour of the condensate in the topological sectors considered agrees, within our stati...

  6. Complex Langevin for Lattice QCD at $T=0$ and $\\mu \\ge 0$

    CERN Document Server

    Sinclair, D K

    2016-01-01

    QCD at finite quark-/baryon-number density, which describes nuclear matter, has a sign problem which prevents direct application of standard simulation methods based on importance sampling. When such finite density is implemented by the introduction of a quark-number chemical potential $\\mu$, this manifests itself as a complex fermion determinant. We apply simulations using the Complex Langevin Equation (CLE) which can be applied in such cases. However, this is not guaranteed to give correct results, so that extensive tests are required. In addition, gauge cooling is required to prevent runaway behaviour. We test these methods on 2-flavour lattice QCD at zero temperature on a small ($12^4$) lattice at an intermediate coupling $\\beta=6/g^2=5.6$ and relatively small quark mass $m=0.025$, over a range of $\\mu$ values from $0$ to saturation. While this appears to show the correct phase structure with a phase transition at $\\mu \\approx m_N/3$ and a saturation density of $3$ at large $\\mu$, the observables show dep...

  7. High-energy hadron-hadron (dipole-dipole) scattering from lattice QCD

    CERN Document Server

    Giordano, M

    2008-01-01

    In this paper the problem of the high-energy hadron-hadron (dipole-dipole) scattering is approached (for the first time) from the point of view of lattice QCD, by means of Monte Carlo numerical simulations. In the first part, we give a brief review of how high-energy scattering amplitudes can be reconstructed, using a functional integral approach, in terms of certain correlation functions of two Wilson loops and we also briefly recall some relevant analyticity and crossing-symmetry properties of these loop-loop correlation functions, when going from Euclidean to Minkowskian theory. In the second part, we shall see how these (Euclidean) loop-loop correlation functions can be evaluated in lattice QCD and we shall compare our numerical results with some nonperturbative analytical estimates appeared in the literature, discussing in particular the question of the analytic continuation from Euclidean to Minkowskian theory and its relation to the still unsolved problem of the asymptotic s-dependence of the hadron-ha...

  8. 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

  9. 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.

  10. 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.)

  11. Valence quark contribution for the gamma N -> Delta quadrupole transition extracted from lattice QCD

    CERN Document Server

    Ramalho, G

    2009-01-01

    Starting with a spectator quark model developed for the nucleon (N) and the Delta in the physical pion mass region, we extend the predictions of the reaction gamma N -> Delta to the lattice QCD regime. The quark model includes S and D waves in the quark-diquark wavefunctions. Within this framework it is the D-wave part in the Delta wavefunction that generates nonzero valence contributions for the quadrupole form factors of the transition. Those contributions are however insufficient to explain the physical data, since the pion cloud contributions dominate. To separate the two effects we apply the model to the lattice regime in a region where the pion cloud effects are negligible, and adjust the D-state parameters directly to the lattice data. This process allows us to obtain a better determination of the D-state contributions. Finally, by adding a simple parametrization of the pion cloud we establish the connection between the experimental data and the lattice data.

  12. Valence quark contribution for the gamma N -> Delta quadrupole transition extracted from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Ramalho, Gilberto; Haderer De La Pena S, Maria

    2009-01-01

    Starting with a spectator quark model developed for the nucleon (N) and the Delta in the physical pion mass region, we extend the predictions of the reaction gamma N -> Delta to the lattice QCD regime. The quark model includes S and D waves in the quark-diquark wavefunctions. Within this framework it is the D-wave part in the Delta wavefunction that generates nonzero valence contributions for the quadrupole form factors of the transition. Those contributions are however insufficient to explain the physical data, since the pion cloud contributions dominate. To separate the two effects we apply the model to the lattice regime in a region where the pion cloud effects are negligible, and adjust the D-state parameters directly to the lattice data. This process allows us to obtain a better determination of the D-state contributions. Finally, by adding a simple parametrization of the pion cloud we establish the connection between the experimental data and the lattice da

  13. Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD

    Science.gov (United States)

    Braun-Munzinger, P.; Kalweit, A.; Redlich, K.; Stachel, J.

    2016-12-01

    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 √{sNN} = 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 Tc ≃ 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 μB = 0, the comparisons with LHC data are the most direct due to the vanishing baryon transport to midrapidity at these high energies.

  14. NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.

    Energy Technology Data Exchange (ETDEWEB)

    LIN H.-W.; OHTA, S.

    2006-10-02

    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{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments {sub u-d}/{sub {Delta}u-{Delta}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 a{sup -1} {approx} 1.6GeV and the spatial volume is about (3.0fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and {sub u-d}/{sub {Delta}u-{Delta}d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.

  15. Two-nucleon higher partial-wave scattering from lattice QCD

    Science.gov (United States)

    Berkowitz, Evan; Kurth, Thorsten; Nicholson, Amy; Joó, Bálint; Rinaldi, Enrico; Strother, Mark; Vranas, Pavlos M.; Walker-Loud, André

    2017-02-01

    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 fm) 3 and V ≈(4.6 fm) 3 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.

  16. The Neutral kaon mixing parameter B(K) from unquenched mixed-action lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Christopher Aubin, Jack Laiho, Ruth S. Van de Water

    2010-01-01

    We calculate the neutral kaon mixing parameter B{sub K} in unquenched lattice QCD using asqtad-improved staggered sea quarks and domain-wall valence quarks. We use the '2+1' flavor gauge configurations generated by the MILC Collaboration, and simulate with multiple valence and sea quark masses at two lattice spacings of a {approx} 0.12 fm and a {approx} 0.09 fm. We match the lattice determination of B{sub K} to the continuum value using the nonperturbative method of Rome-Southampton, and extrapolate B{sub K} to the continuum and physical quark masses using mixed action chiral perturbation theory. The 'mixed-action' method enables us to control all sources of systematic uncertainty and therefore to precisely determine B{sub K}; we find a value of B{sub K}{sup {ovr MS},NDR} (2 GeV) = 0.527(6)(21), where the first error is statistical and the second is systematic.

  17. Lattice QCD study of the Boer-Mulders effect in a pion

    CERN Document Server

    Engelhardt, M; Musch, B; Negele, J; Schäfer, A

    2015-01-01

    The three-dimensional momenta of quarks inside a hadron are encoded in transverse momentum-dependent parton distribution functions (TMDs). This work presents an exploratory lattice QCD study of a TMD observable in the pion describing the Boer-Mulders effect, which is related to polarized quark transverse momentum in an unpolarized hadron. Particular emphasis is placed on the behavior as a function of a Collins-Soper evolution parameter quantifying the relative rapidity of the struck quark and the initial hadron, e.g., in a semi-inclusive deep inelastic scattering (SIDIS) process. The lattice calculation, performed at the pion mass m_pi = 518 MeV, utilizes a definition of TMDs via hadronic matrix elements of a quark bilocal operator with a staple-shaped gauge connection; in this context, the evolution parameter is related to the staple direction. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. I...

  18. Light meson electromagnetic form factors from three-flavor lattice QCD with exact chiral symmetry

    CERN Document Server

    Aoki, S; Feng, X; Hashimoto, S; Kaneko, T; Noaki, J; Onogi, T

    2015-01-01

    We study the chiral behavior of the electromagnetic (EM) form factors of pion and kaon in three-flavor lattice QCD. In order to make a direct comparison of the lattice data with chiral perturbation theory (ChPT), we employ the overlap quark action that has exact chiral symmetry. Gauge ensembles are generated at a lattice spacing of 0.11 fm with four pion masses ranging between M_pi \\simeq 290 MeV and 540 MeV and with a strange quark mass m_s close to its physical value. We utilize the all-to-all quark propagator technique to calculate the EM form factors with high precision. Their dependence on m_s and on the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields, respectively. A detailed comparison with SU(2) and SU(3) ChPT reveals that the next-to-next-to-leading order terms in the chiral expansion are important to describe the chiral behavior of the form factors in the pion mass range studied in this work. We estimate the relevant low-energy...

  19. B- and D-meson decay constants from three-flavor lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Bazavov, A. [Brookhaven National Laboratory (BNL), Upton, NY (United States); et al.

    2012-06-01

    We calculate the leptonic decay constants of B_{(s)} and D_{(s)} mesons in lattice QCD using staggered light quarks and Fermilab bottom and charm quarks. We compute the heavy-light meson correlation functions on the MILC asqtad-improved staggered gauge configurations which include the effects of three light dynamical sea quarks. We simulate with several values of the light valence- and sea-quark masses (down to ~m_s/10) and at three lattice spacings (a ~ 0.15, 0.12, and 0.09 fm) and extrapolate to the physical up and down quark masses and the continuum using expressions derived in heavy-light meson staggered chiral perturbation theory. We renormalize the heavy-light axial current using a mostly nonperturbative method such that only a small correction to unity must be computed in lattice perturbation theory and higher-order terms are expected to be small. We obtain f_{B^+} = 196.9(8.9) MeV, f_{B_s} = 242.0(9.5) MeV, f_{D^+} = 218.9(11.3) MeV, f_{D_s} = 260.1(10.8) MeV, and the SU(3) flavor-breaking ratios f_{B_s}/f_{B} = 1.229(26) and f_{D_s}/f_{D} = 1.188(25), where the numbers in parentheses are the total statistical and systematic uncertainties added in quadrature.

  20. Magnetic susceptibility of QCD at zero and at finite temperature from the lattice

    CERN Document Server

    Bali, G S; Constantinou, M; Costa, M; Endrodi, G; Katz, S D; Panagopoulos, H; Schaefer, A

    2012-01-01

    The response of the QCD vacuum to a constant external (electro)magnetic field is studied through the tensor polarization of the chiral condensate and the magnetic susceptibility at zero and at finite temperature. We determine these quantities using lattice configurations generated with the tree-level Symanzik improved gauge action and N_f=1+1+1 flavors of stout smeared staggered quarks with physical masses. We carry out the renormalization of the observables under study and perform the continuum limit both at T>0 and at T=0, using different lattice spacings. Finite size effects are studied by using various spatial lattice volumes. The magnetic susceptibilities \\chi_f reveal a diamagnetic behavior; we obtain at zero temperature \\chi_u=-(2.08 +/- 0.08) 1/GeV^2, \\chi_d=-(2.02 +/- 0.09) 1/GeV^2 and \\chi_s=-(3.4 +/- 1.4) 1/GeV^2 for the up, down and strange quarks, respectively, in the MSBar scheme at a renormalization scale of 2 GeV. We also find the polarization to change smoothly with the temperature in the con...

  1. The bottomonium spectrum at finite temperature from $N_f=2+1$ lattice QCD

    CERN Document Server

    Aarts, Gert; Harris, Tim; Kim, Seyong; Lombardo, Maria Paola; Ryan, Sinéad M; Skullerud, Jon-Ivar

    2014-01-01

    We present results on the bottomonium spectrum at temperatures above and below the deconfinement crossover temperature, $T_c$, from dynamical lattice QCD simulations. The heavy quark is treated with a non-relativistic effective field theory on the lattice and serves as a probe of the hot medium. Ensembles with a finer spatial lattice spacing and a greater range of temperatures below $T_c$ than those previously employed by this collaboration are used. In addition, there are $N_f=2+1$ flavours of Wilson clover quark in the sea with $M_\\pi\\approx400$ MeV and we perform a more careful tuning of the bottom quark mass in this work. We calculate the spectral functions of S and P wave bottomonium states using the maximum entropy method and confirm earlier findings on the survival of the ground state S wave states up to at least $2T_c$ and the immediate dissociation of the P wave states above $T_c$.

  2. Up and Down Quark Masses and Corrections to Dashen's Theorem from Lattice QCD and Quenched QED.

    Science.gov (United States)

    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.

  3. 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.

  4. 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.

  5. Up and Down Quark Masses and Corrections to Dashen's Theorem from Lattice QCD and Quenched QED

    Science.gov (United States)

    Fodor, Z.; Hoelbling, C.; Krieg, S.; Lellouch, L.; Lippert, Th.; Portelli, A.; Sastre, A.; Szabo, K. K.; Varnhorst, L.; Budapest-Marseille-Wuppertal Collaboration

    2016-08-01

    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 Nf=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 ɛ =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, mu=2.27 (6 )(5 )(4 ) and md=4.67 (6 )(5 )(4 ) MeV in the modified minimal subtraction scheme at 2 G e V and the isospin breaking ratios mu/md=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 mu=0 solution to the strong C P problem by more than 24 standard deviations.

  6. Light meson electromagnetic form factors from three-flavor lattice QCD with exact chiral symmetry

    Science.gov (United States)

    Aoki, S.; Cossu, G.; Feng, X.; Hashimoto, S.; Kaneko, T.; Noaki, J.; Onogi, T.

    2016-02-01

    We study the chiral behavior of the electromagnetic (EM) form factors of pions and kaons in three-flavor lattice QCD. In order to make a direct comparison of the lattice data with chiral perturbation theory (ChPT), we employ the overlap quark action that has exact chiral symmetry. Gauge ensembles are generated at a lattice spacing of 0.11 fm with four pion masses ranging between Mπ≃290 MeV and 540 MeV and with a strange quark mass ms close to its physical value. We utilize the all-to-all quark propagator technique to calculate the EM form factors with high precision. Their dependence on ms and on the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields, respectively. A detailed comparison with SU(2) and SU(3) ChPT reveals that the next-to-next-to-leading order terms in the chiral expansion are important to describe the chiral behavior of the form factors in the pion mass range studied in this work. We estimate the relevant low-energy constants and the charge radii, and find reasonable agreement with phenomenological and experimental results.

  7. Iso-vector and Iso-scalar Tensor Charges of the Nucleon from Lattice QCD

    CERN Document Server

    Bhattacharya, Tanmoy; Cohen, Saul; Gupta, Rajan; Joseph, Anosh; Lin, Huey-Wen; Yoon, Boram

    2015-01-01

    We present results for the iso-vector and flavor diagonal tensor charges $g^{u-d}_T$, $g^{u}_T$, $g^{d}_T$, and $g^{s}_T$ needed to probe novel tensor interactions at the TeV scale in neutron and nuclear $\\beta$-decays and the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice QCD calculations were done using nine ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings $a \\approx 0.06, 0.09$ and $0.12 $ fm and three quark masses corresponding to the pion masses $M_\\pi \\approx 130, 220$ and $310 $ MeV. Using estimates from these ensembles, we quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, volume and light quark masses for the connected contributions. The final estimates of the connected nucleon (proton) tensor charge for the iso-vector combination is $g_T^{u-d} = 1.020(76) $ in the $\\overline{\\text{MS}}$ scheme ...

  8. PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP, HADRON STRUCTURE FROM LATTICE QCD, MARCH 18 - 22, 2002, BROOKHAVEN NATIONAL LABORATORY.

    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.

  9. Improving the Volume Dependence of Two-Body Binding Energies Calculated with Lattice QCD

    CERN Document Server

    Davoudi, Zohreh

    2011-01-01

    Volume modifications to the binding of two-body systems in large cubic volumes of extent L depend upon the total momentum and exponentially upon the ratio of L to the size of the boosted system. Recent work by Bour et al determined the momentum dependence of the leading volume modifications to nonrelativistic systems with periodic boundary conditions imposed on the single-particle wavefunctions, enabling them to numerically determine the scattering of such bound states using a low-energy effective field theory and Luschers finite-volume method. The calculation of bound nuclear systems directly from QCD using Lattice QCD has begun, and it is important to reduce the systematic uncertainty introduced into such calculations by the finite spatial extent of the gauge-field configurations. We extend the work of Bour et al from nonrelativistic quantum mechanics to quantum field theory by generalizing the work of Luscher and of Gottlieb and Rummukainen to boosted two-body bound states. The volume modifications to bind...

  10. Refining new-physics searches in B -> D tau nu decay with lattice QCD

    CERN Document Server

    Bailey, Jon A; Bernard, C; Bouchard, C M; DeTar, C; Du, Daping; El-Khadra, A X; Foley, J; Freeland, E D; Gamiz, E; Gottlieb, Steven; Heller, U M; Kim, Jongjeong; Kronfeld, A S; Laiho, J; Levkova, L; Mackenzie, P B; Meurice, Y; Neil, E T; Oktay, M B; Qiu, Si-Wei; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, Ran

    2012-01-01

    The semileptonic decay channel B -> D tau nu is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently the BaBar experiment reported the first observation of the exclusive semileptonic decay B -> D tau nu, finding an approximately 2-sigma discrepancy with the Standard-Model prediction for the ratio R(D)=BR(B -> D tau nu)/BR(B -> l nu), where l=e,mu. We compute this ratio of branching fractions using hadronic form factors computed in unquenched lattice QCD and obtain R(D) = 0.316(12)(7), where the errors are statistical and total systematic, respectively. This result is the first Standard-Model calculation of R(D) from ab initio full QCD. It agrees with previous theoretical estimates, but the errors are smaller primarily due to the reduced uncertainty in the scalar form factor f_0(q^2). We also compute R(D) in models with electrically charged scalar exchange, such as the type II two-Higgs doublet model (2HDM). Our result disagrees significantly with previous est...

  11. Polyakov loop effects on the phase diagram in strong-coupling lattice QCD

    CERN Document Server

    Miura, Kohtaroh; Nakano, Takashi Z; Ohnishi, Akira

    2016-01-01

    We investigate the Polyakov loop effects on the QCD phase diagram by using the strong-coupling (1/g^2) expansion of the lattice QCD (SC-LQCD) with one species of unrooted staggered quark, including O}(1/g^4) effects. We take account of the effects of Polyakov loop fluctuations in Weiss mean-field approximation (MFA), and compare the results with those in the Haar-measure MFA (no fluctuation from the mean-field). The Polyakov loops strongly suppress the chiral transition temperature in the second-order/crossover region at small chemical potential, while they give a minor modification of the first-order phase boundary at larger chemical potential. The Polyakov loops also account for a drastic increase of the interaction measure near the chiral phase transition. The chiral and Polyakov loop susceptibilities have their peaks close to each other in the second-order/crossover region. In particular in Weiss MFA, there is no indication of the separated deconfinement transition boundary from the chiral phase boundary ...

  12. Octet Baryon Magnetic Moments from Lattice QCD: Approaching Experiment from the Three-Flavor Symmetric Point

    CERN Document Server

    Parreno, Assumpta; Tiburzi, Brian C; Wilhelm, Jonas; Chang, Emmanuel; Detmold, William; Orginos, Kostas

    2016-01-01

    Lattice QCD calculations with background magnetic fields are used to determine the magnetic moments of the octet baryons. Computations are performed at the physical value of the strange quark mass, and two values of the light quark mass, one corresponding to the SU(3) flavor-symmetric point, where the pion mass is ~ 800 MeV, and the other corresponding to a pion mass ~ 450 MeV. The moments are found to exhibit only mild pion-mass dependence when expressed in terms of appropriately chosen magneton units---the natural baryon magneton. This suggests that simple extrapolations can be used to determine magnetic moments at the physical point, and extrapolated results are found to agree with experiment within uncertainties. A curious pattern is revealed among the anomalous baryon magnetic moments which is linked to the constituent quark model, however, careful scrutiny exposes additional features. Relations expected to hold in the large-Nc limit of QCD are studied; and, in one case, the quark model prediction is sig...

  13. New exact solutions of hydrodynamics for rehadronizing fireballs with lattice QCD equation of state

    CERN Document Server

    Csörgő, T

    2016-01-01

    We describe fireballs that rehadronize from a perfectly fluid quark matter to a chemically frozen, multi-component hadron gas. In the hydrodynamics of these fireballs, we utilize the lattice QCD equation of state, however, we also apply non-relativistic kinematics for simplicity and clarity. Two new classes of exact, analytic solutions of fireball hydrodynamics are presented: the first class describes triaxially expanding, non-rotating ellipsoidal fireballs, while the second class of exact solutions corresponds to spheroidally symmetric, rotating fireballs. In both classes of solutions, we find evidence for a secondary explosion, that happens just after hadrochemical freeze-out. A realistic, linear mass scaling of the slope parameters of the single particle spectra of various hadronic species is obtained analytically, as well as an also realistic, linear mass scaling of the inverse of the squared HBT radius parameters of the Bose-Einstein correlation functions.

  14. A quasi-particle description of $(2+1)$- flavor lattice QCD equation of state

    CERN Document Server

    Chandra, Vinod

    2011-01-01

    A quasi-particle model has been employed to describe the $(2+1)$-flavor lattice QCD equation of state with physical quark masses. The interaction part of the equation of state has been mapped to the effective fugacities of otherwise non-interacting quasi-gluons and quasi-quarks. The mapping is found to be exact for the equation of state. The model leads to non-trivial dispersion relations for quasi-partons. The dispersion relations, effective quasi-particle number densities, and trace anomaly have been investigated employing the model. A Virial expansion for the EOS has further been obtained to investigate the role of interactions in quark-gluon plasma (QGP). Finally, Debye screening in QGP has been studied employing the model.

  15. Domain decomposition, multi-level integration and exponential noise reduction in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Ce, Marco [Scuola Normale Superiore, Pisa (Italy); INFN, Sezione di Pisa (Italy); Giusti, Leonardo [Univ. di Milano-Bicocca (Italy). Dipt. di Fisica; INFN, Sezione di Milano-Bicocca (Italy); Schaefer, Stefan [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2016-01-15

    We explore the possibility of computing fermionic correlators on the lattice by combining a domain decomposition with a multi-level integration scheme. The quark propagator is expanded in series of terms with a well defined hierarchical structure. The higher the order of a term, the (exponentially) smaller its magnitude, the less local is its dependence on the gauge field. Once inserted in a Wick contraction, the gauge-field dependence of the terms in the resulting series can be factorized so that it is suitable for multi-level Monte Carlo integration. We test the strategy in quenched QCD by computing the disconnected correlator of two flavor-diagonal pseudoscalar densities, and a nucleon two-point function. In either cases we observe a significant exponential increase of the signal-to-noise ratio.

  16. Results for the Etaprime Mass from Two-Flavor Lattice QCD

    CERN Document Server

    Lesk, V I; Fukugita, M; Ishikawa, K I; Ishizuka, N; Iwasaki, Y; Kanaya, K; Kaneko, T; Kuramashi, Y; Okawa, M; Taniguchi, Y; Ukawa, A; Umeda, T; Yoshié, T

    2002-01-01

    We present results for the mass of the etaprime 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 csw. Measurements are made at three couplings corresponding to a approx. 0.22, 0.16, 0.11 fm for four quark masses corresponding to mpi over mrho approx. 0.8, 0.75, 0.7, 0.6. Thw 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 etaprime channel. We obtain metaprime=0.960(87)+0.036-0.286GeV in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations.

  17. Baryon-baryon bound states in a (2+1)-dimensional lattice QCD model

    Science.gov (United States)

    Faria da Veiga, Paulo A.; O'Carroll, Michael; Schor, Ricardo

    2003-08-01

    We consider bound states of two baryons (antibaryons) in lattice QCD in a Euclidean formulation. For simplicity, we analyze an SU(3) theory with a single flavor in 2+1 dimensions and two-dimensional Dirac matrices. For a small hopping parameter 0<κ≪1 and large glueball mass, we recently showed the existence of a (anti)baryonlike particle, with an asymptotic mass of the order of -3 ln κ and with an isolated dispersion curve, i.e., an upper gap property persisting up to near the meson-baryon threshold, which is of order -5 ln κ. Here, we show that there is no baryon-baryon (or antibaryon-antibaryon) bound state solution to the Bethe-Salpeter equation up to the two-baryon threshold, which is approximately -6 ln κ.

  18. Lattice QCD ensembles with four flavors of highly improved staggered quarks

    CERN Document Server

    Bazavov, A; DeTar, C; Freeman, W; Gottlieb, Steven; Heller, U M; Hetrick, J E; Komijani, J; Laiho, J; Levkova, L; Osborn, J; Sugar, R L; Toussaint, D; Van de Water, R S; Zhou, Ran

    2013-01-01

    We present results from our simulations of quantum chromodynamics (QCD) with four flavors of quarks: u, d, s, and c. These simulations are performed with a one-loop Symanzik improved gauge action, and the highly improved staggered quark (HISQ) action. We are generating gauge configurations with four values of the lattice spacing ranging from 0.06 fm to 0.15 fm, and three values of the light quark mass, including the value for which the Goldstone pion mass is equal to the physical pion mass. We discuss simulation algorithms, scale setting, taste symmetry breaking, and the autocorrelations of various quantities. We also present results for the topological susceptibility which demonstrate the improvement of the HISQ configurations relative to those generated earlier with the asqtad improved staggered action.

  19. Electric Dipole Moment of the Neutron from 2+1 Flavor Lattice QCD.

    Science.gov (United States)

    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).

  20. What lattice QCD spectral functions can tell us about heavy quarkonium in the QGP

    CERN Document Server

    Rothkopf, Alexander

    2016-01-01

    The bound states of a heavy quark and antiquark ($c\\bar{c}, b\\bar{b}$) are ideal probes to explore the quark-gluon plasma created in relativistic heavy-ion collisions at the RHIC and LHC. Not only have they become experimentally accessible with high precision but also efficient tools, so called effective field theories (EFT) have been developed to treat them theoretically. Here we present recent progress in understanding the in-medium behavior of heavy-quarkonium with the help of EFT's combined with non-perturbative and first principles simulations in lattice QCD. In particular we discuss computations of heavy quarkonium spectral functions with the help of Bayesian unfolding methods and the physics we can extract from them. Limitations and the underlying assumptions of the used approaches are pointed out.

  1. In-medium P-wave quarkonium from the complex lattice QCD potential

    Science.gov (United States)

    Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

    2016-10-01

    We extend our lattice QCD potential based study [1] 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.

  2. Onset transition to cold nuclear matter from lattice QCD with heavy quarks.

    Science.gov (United States)

    Fromm, M; Langelage, J; Lottini, S; Neuman, M; Philipsen, O

    2013-03-22

    Lattice QCD at finite density suffers from a severe sign problem, which has so far prohibited simulations of the cold and dense regime. Here we study the onset of nuclear matter employing a three-dimensional effective theory derived by combined strong coupling and hopping expansions, which is valid for heavy but dynamical quarks and has a mild sign problem only. Its numerical evaluations agree between a standard Metropolis and complex Langevin algorithm, where the latter is free of the sign problem. Our continuum extrapolated data approach a first order phase transition at μ(B) ≈ m(B) as the temperature approaches zero. An excellent description of the data is achieved by an analytic solution in the strong coupling limit.

  3. Magnetic catalysis (and inverse catalysis) at finite temperature in two-color lattice QCD

    CERN Document Server

    Ilgenfritz, E -M; Petersson, B; Schreiber, A

    2013-01-01

    Two-color lattice QCD with N_f=4 staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge q is studied in a homogeneous magnetic background field B and at non-zero temperature T. In order to circumvent renormalization as a function of the bare coupling we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudo-scalar meson mass (m_pi \\approx 175 MeV \\approx T_c(B=0)) we confirm magnetic catalysis for sufficiently strong magnetic field strength, while at T=195 MeV and weak magnetic field (qB {\\lesssim} 0.8 GeV^2) we find a rise of the Polyakov loop with qB and thus, indications for an inverse magnetic catalysis.

  4. In-medium quarkonium properties from a lattice QCD based effective field theory

    Science.gov (United States)

    Kim, Seyong; Petreczky, Peter; Rothkopf, Alexander

    2016-12-01

    In order to understand the experimental data on heavy quarkonium production in heavy ion collisions at RHIC and LHC it is necessary (though not sufficient) to pinpoint the properties of heavy Q Q ‾ bound states in the deconfined quark-gluon plasma, including their dissolution. Here we present recent results on the temperature dependence of bottomonium and charmonium correlators, as well as their spectral functions in a lattice QCD based effective field theory called NRQCD, surveying temperatures close to the crossover transition 140MeV < T < 249MeV. The spectra are reconstructed based on a novel Bayesian prescription, whose systematic uncertainties are assessed. We present indications for sequential melting of different quarkonium species with respect to their vacuum binding energies and give estimates on the survival of S-wave and P-wave ground states.

  5. 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

  6. Lattice thermal expansion and anisotropic displacements in -sulfur from diffraction experiments and first-principles theory.

    Science.gov (United States)

    George, Janine; Deringer, Volker L; Wang, Ai; Müller, Paul; Englert, Ulli; Dronskowski, Richard

    2016-12-21

    Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S8), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

  7. A study on the optimization of finite volume effects of B K in lattice QCD by using the CUDA

    Science.gov (United States)

    Kim, Jangho; Cho, Kihyeon

    2015-07-01

    Lattice quantum chromodynamics (QCD) is the non-perturbative implementation of field theory to solve the QCD theory of quarks and gluons by using the Feynman path integral approach. We calculate the kaon CP (charge-parity) violation parameter B K generally arising in theories of physics beyond the Standard Model. Because lattice simulations are performed on finite volume lattices, the finite volume effects must be considered to exactly estimate the systematic error. The computational cost of numerical simulations may increase dramatically as the lattice spacing is decreased. Therefore, lattice QCD calculations must be optimized to account for the finite volume effects. The methodology used in this study was to develop an algorithm to parallelize the code by using a graphic processing unit (GPU) and to optimize the code to achieve as close to the theoretical peak performance as possible. The results revealed that the calculation speed of the newly-developed algorithm is significantly improved compared with that of the current algorithm for the finite volume effects.

  8. The nucleon mass and pion-nucleon sigma term from a chiral analysis of Nf=2 lattice QCD world data

    CERN Document Server

    Alvarez-Ruso, L; Camalich, J Martin; Vacas, M J Vicente

    2014-01-01

    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 Delta(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 Delta(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 sigma pi-N lQCD data point near Mpi = 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 41(5)(4) MeV for the sigma pi-N term in the 2 flavor case and 52(3)(8) MeV in the 2+1 flavors case.

  9. 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.

  10. A study of symmetry restoration at finite temperature in the O(4) model using anisotropic lattices

    Science.gov (United States)

    Gavai, R. V.; Heller, U. M.; Karsch, F.; Plache, B.; Neuhaus, T.

    Results of investigations of the O(4) spin model at finite temperature using anisotropic lattices are presented. In both the large N approximation and the numerical simulations using the Wolff cluster algorithm we find that the ratio of the symmetry restoration temperature TSR to the Higgs mass mH is independent of the anisotropy. We obtain a lower bound of 0.59 ± 0.04 for the ratio, T SR/m H, at m H ⋍ 0.5 , which is lowered furhter by about 10% at m Ha ⋍ 1 .

  11. A study of symmetry restoration at finite temperature in the O(4) model using anisotropic lattices

    CERN Document Server

    Gavai, R V; Karsch, Frithjof; Plache, B; Neuhaus, T

    1992-01-01

    Results of investigations of the $O(4)$ spin model at finite temperature using anisotropic lattices are presented. In both the large $N$ approximation and the numerical simulations using the Wolff cluster algorithm we find that the ratio of the symmetry restoration temperature $T_{\\rm SR}$ to the Higgs mass $m_{\\rm H}$ is independent of the anisotropy. We obtain a lower bound of $0.59 \\pm 0.04$ for the ratio, $T_{\\rm SR}/m_{\\rm H}$, at $m_{\\rm H}a \\simeq 0.5$, which is lowered further by about $10 \\%$ at $m_{\\rm H}a \\simeq 1.$

  12. Individual complex Dirac eigenvalue distributions from random matrix theory and comparison to quenched lattice QCD with a quark chemical potential.

    Science.gov (United States)

    Akemann, G; Bloch, J; Shifrin, L; Wettig, T

    2008-01-25

    We analyze how individual eigenvalues of the QCD Dirac operator at nonzero quark chemical potential are distributed in the complex plane. Exact and approximate analytical results for both quenched and unquenched distributions are derived from non-Hermitian random matrix theory. When comparing these to quenched lattice QCD spectra close to the origin, excellent agreement is found for zero and nonzero topology at several values of the quark chemical potential. Our analytical results are also applicable to other physical systems in the same symmetry class.

  13. Hall Effect in the Vortex Lattice of d-Wave Superconductors with Anisotropic Fermi Surfaces

    Science.gov (United States)

    Kohno, Wataru; Ueki, Hikaru; Kita, Takafumi

    2017-02-01

    On the basis of the augmented quasiclassical theory of superconductivity with the Lorentz force, we study the magnetic field dependence of the charge distribution due to the Lorentz force in a d-wave vortex lattice with anisotropic Fermi surfaces. Owing to the competition between the energy-gap and Fermi surface anisotropies, the charge profile in the vortex lattice changes dramatically with increasing magnetic field because of the overlaps of each nearest vortex-core charge. In addition, the accumulated charge in the core region may reverse its sign as a function of magnetic field. This strong field dependence of the vortex-core charge cannot be observed in the model with an isotropic Fermi surface.

  14. Stochastic propagators for multi-pion correlation functions in lattice QCD with GPUs

    CERN Document Server

    Giedt, Joel

    2014-01-01

    Motivated by the application of L\\"uscher's finite volume method to the study of the lightest scalar resonance in the $\\pi\\pi \\to \\pi\\pi$ isoscalar channel, in this article we describe our studies of multi-pion correlation functions computed using stochastic propagators in quenched lattice QCD, harnessing GPUs for acceleration. We consider two methods for constructing the correlation functions. One "outer product" approach becomes quite expensive at large lattice extent $L$, having an ${\\cal O}(L^7)$ scaling. The other "stochastic operator" approach scales as ${\\cal O}(N_r^2 L^4)$, where $N_r$ is the number of random sources. It would become more efficient if variance reduction techniques are used and the volume is fairly large. It is also found that correlations between stochastic propagators appearing in the same diagram, when a single set of random source vectors is used, lead to much larger errors than if separate random sources are used for each propagator. The calculations involve states with quantum nu...

  15. Flavor Singlet Meson Mass in the Continuum Limit in Two-Flavor Lattice QCD

    CERN Document Server

    Aoki, S; Fukugita, M; Ishikawa, K; Iwasaki, Y; Kanaya, K; Kuramashi, Y; Lesk, V I; Okawa, M; Taniguchi, Y; Ukawa, A; Umeda, T; Yoshié, T

    2003-01-01

    We present results for the mass of the eta-prime meson in the continuum limit for two-flavor lattice QCD, calculated on the CP-PACS computer, using a renormalization-group improved gauge action, and Sheikholeslami and Wohlert's fermion action with tadpole-improved csw. Correlation functions are measured at three values of the coupling constant beta corresponding to the lattice spacing a approx. 0.22, 0.16, 0.11 fm and for four values of the quark mass parameter kappa corresponding to mpi over mrho approx. 0.8, 0.75, 0.7 and 0.6. For each beta, kappa pair, 400-800 gauge configurations are used. The two-loop diagrams are evaluated using a noisy source method. We calculate eta-prime propagators using local sources, and find that excited state contributions are much reduced by smearing. A full analysis for the smeared propagators gives metaprime=0.960(87)+0.036-0.248 GeV, in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and con...

  16. Colored-hadron distribution in hadron scattering in SU(2) lattice QCD

    CERN Document Server

    Takahashi, Toru T

    2016-01-01

    In color SU(2) lattice QCD, we investigate colored-diquark distributions in two-hadron scatterings by means of Bethe-Salpeter amplitudes on the lattice. With colored-diquark operators in the Coulomb gauge, we measure components of two colored diquarks realized as intermediate states via one gluon exchange (OGE) processes in hadron scattering. From the colored-diquark distributions, we estimate the dominant range of gluon (color) exchanges between closely located two hadrons. We find that the colored-diquark components are enhanced at the short range ($\\leq$0.2 fm) and their tails show the single-exponential damping. In order to distinguish the genuine colored-diquark components originating in the color exchange processes from trivial colored two-quark components contained in two color-singlet hadrons as a result of simple transformation of hadronic basis, we repeat the analyses on the artificially constructed gauge fields, where low- and high-momentum gluon components are decoupled and only restricted pair of...

  17. Light-cone Distribution Amplitudes of the Nucleon and Negative Parity Nucleon Resonances from Lattice QCD

    CERN Document Server

    Braun, V M; Gläßle, B; Göckeler, M; Schäfer, A; Schiel, R W; Söldner, W; Sternbeck, A; Wein, P

    2014-01-01

    We present the results of a lattice study of light-cone distribution amplitudes (DAs) of the nucleon and negative parity nucleon resonances using two flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to m_pi = 150 MeV. We find that the three valence quarks in the proton share their momentum in the proportion 37% : 31% : 31%, where the larger fraction corresponds to the u-quark that carries proton helicity, and determine the value of the wave function at the origin in position space, which turns out to be small compared to the existing estimates based on QCD sum rules. Higher-order moments are constrained by our data and are all compatible with zero within our uncertainties. We also calculate the normalization constants of the higher-twist DAs that are related to the distribution of quark angular momentum. Furthermore, we use the variational method and customized parity projection operators to study the states with negative parity. In this way we are able to separate ...

  18. Pion-nucleon scattering in the Roper channel from lattice QCD

    CERN Document Server

    Lang, C B; Padmanath, M; Prelovsek, S

    2016-01-01

    We present a lattice QCD study of $N\\pi$ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance $N^*(1440)$ resides in experiment. The study is based on the PACS-CS ensemble of gauge configurations with $N_f=2+1$ Wilson-clover dynamical fermions, $m_\\pi \\simeq 156~$MeV and $L\\simeq 2.9~$fm. In addition to a number of $qqq$ interpolating fields, we implement operators for $N\\pi$ in $p$-wave and $N\\sigma$ in $s$-wave. In the center-of-momentum frame we find three eigenstates below 1.65 GeV. They are dominated by $N(0)$, $N(0)\\pi(0)\\pi(0)$ and $N(p)\\pi(-p)$ with $p\\simeq 2\\pi/L$, where momenta are given in parentheses. This is the first simulation where the expected multi-hadron states are found in this channel. The experimental $N\\pi$ phase-shift would -- in the approximation of purely elastic $N\\pi$ scattering -- imply an additional eigenstate near the Roper mass $m_R\\simeq 1.43~$GeV for our lattice size. We do not observe any such additional eigenstate, which indicates that $N\\p...

  19. $B^0_{(s)}$-mixing matrix elements from lattice QCD for the Standard Model and beyond

    CERN Document Server

    Bazavov, A; Bouchard, C M; Chang, C C; DeTar, C; Du, Daping; El-Khadra, A X; Freeland, E D; Gamiz, E; Gottlieb, Steven; Heller, U M; Kronfeld, A S; Laiho, J; Mackenzie, P B; Neil, E T; Simone, J; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, Ran

    2016-01-01

    We calculate---for the first time in three-flavor lattice QCD---the hadronic matrix elements of all five local operators that contribute to neutral $B^0$- and $B_s$-meson mixing in and beyond the Standard Model. We present a complete error budget for each matrix element and also provide the full set of correlations among the matrix elements. We also present the corresponding bag parameters and their correlations, as well as specific combinations of the mixing matrix elements that enter the expression for the neutral $B$-meson width difference. We obtain the most precise determination to date of the SU(3)-breaking ratio $\\xi = 1.203(17)(6)$, where the second error stems from the omission of charm sea quarks, while the first encompasses all other uncertainties. The threefold reduction in total uncertainty tightens the constraint from $B$ mixing on the Cabibbo-Kobayashi-Maskawa (CKM) unitarity triangle. Our calculation employs gauge-field ensembles generated by the MILC Collaboration with four lattice spacings a...

  20. Pseudoscalar decay constants of kaon and D-mesons from Nf=2 twisted mass Lattice QCD

    CERN Document Server

    Blossier, B; Frezzotti, R; Haas, B; Herdoiza, G; Jansen, K; Lubicz, V; Mescia, F; Palao, D; Shindler, A; Simula, S; Tarantino, C; Urbach, C; Wenger, U

    2009-01-01

    We present the results of a lattice QCD calculation of the pseudoscalar meson decay constants fpi, fK, fD and fDs, performed with Nf=2 dynamical fermions. The simulation is carried out with the tree-level improved Symanzik gauge action and with the twisted mass fermionic action at maximal twist. We have considered for the final analysis three values of the lattice spacing, a~0.10 fm, 0.09 fm and 0.07 fm, with pion masses down to mpi~270 MeV. Our results for the light meson decay constants are fK=158.1(2.4) MeV and fK/fpi=1.210(18). From the latter ratio, by using the experimental determination of Gamma(K-->mu nu_mu (gamma))/ Gamma(pi--> mu nu_mu (gamma)) and the average value of |Vud| from nuclear beta decays, we obtain |Vus|=0.2222(34), in good agreement with the determination from semileptonic Kl3 decays and the unitarity constraint. For the D and Ds meson decay constants we obtain fD=197(9) MeV, fDs=244(8) MeV and fDs/fD=1.24(3). Our result for fD is in good agreement with the CLEO experimental measurement...