Non-perturbative improvement of the anisotropic Wilson QCD action (original) (raw)

Effective field theory for the anisotropic Wilson lattice action

Physical Review D, 2008

We construct the effective field theory appropriate for describing the low energy behavior of anisotropic Wilson lattice actions and the O(a) improved variant thereof. We then apply this effective field theory to the hadron spectrum and dispersion relations, focussing on the corrections due to the anisotropy. We point out an important feature of anisotropic lattices regarding the Aoki-regime; for a given set of fermion masses and spatial lattice spacing, if an isotropic action is in the QCD-phase, this does not guarantee that the anisotropic action is outside the Aoki-regime. This may be important in the tuning of bare parameters for anisotropic lattices using domain-wall and overlap fermions as well as Wilson and O(a)-improved Wilson fermions.

Symanzik Improvement In The Static Quark Potential

1999

A systematic investigation of Symanzic improvement in the gauge field action is performed for the static quark potential in quenched QCD. We consider Symanzik improved gauge field configurations on a 16^3 X 32 lattice with a relatively coarse lattice spacing of 0.165(2)fm. A matched set of standard Wilson gauge configurations is prepared at \beta = 5.74 with the same physical volume and lattice spacing and is studied for comparison. We find that, despite the coarse lattice spacing, the unimproved and less-expensive Wilson action does as well as the Symanzik action in allowing us to extract the static quark potential at large qqbar separations. We have considered novel methods for stepping off-axis in the static quark potential which provides new insights into the extent to which the ground state potential dominates the Wilson loop correlation function.

Free energies of heavy quarks in full-QCD lattice simulations with Wilson-type quark action

Nuclear Physics A, 2009

The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature in lattice QCD with 2+1 flavors of improved Wilson quarks. From the simulations on 32 3 × 12, 10, 8, 6, 4 lattices in the high temperature phase, based on the fixed scale approach, we find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson loop at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the free energy is compared with the results of thermal perturbation theory.

Improved bilinears in lattice QCD with nondegenerate quarks

Physical Review D, 2006

Simulations of lattice QCD with light dynamical quarks are greatly facilitated by the use of improved actions and operators. Calculations are underway using various types of improved fermions—staggered, domain wall/overlap, maximally twisted and improved Wilson fermions. Here we focus on improved Wilson fermions, and investigate how the improvement program can be extended to remove errors proportional to amq (a is the lattice spacing, and mq a generic quark mass) in the realistic case of nondegenerate quark ...

Lattice effective actions and light-quark confinement

Nuclear Physics B - Proceedings Supplements, 1999

The positive-plaquette Manton action at weak coupling is a reasonable action for short-distance phenomena. We propose an iterative scheme for evolving this action into an effective action for longer distance scales. We report on the first step of this scheme in which we have measured "blocked" Creutz ratios with lattice spacing 2a at β = 16 on a 32 4 lattice and have searched for an effective action that yields the same ratios on a 16 4 lattice. We also suggest a mechanism for quark confinement that relies upon the lightness of the u and d quarks and formulate a way of testing it in lattice simulations of QCD.

Finite-size effects in lattice QCD with dynamical Wilson fermions

Physical Review D, 2005

Due to limited computing resources choosing the parameters for a full lattice QCD simulation always amounts to a compromise between the competing objectives of a lattice spacing as small, quarks as light, and a volume as large as possible. Aiming at pushing unquenched simulations with the standard Wilson action towards the computationally expensive regime of small quark masses, the GRAL project addresses the question whether computing time can be saved by sticking to lattices with rather modest numbers of grid sites and extrapolating the finite-volume results to the infinite volume (prior to the usual chiral and continuum extrapolations). In this context we investigate in this work finite-size effects in simulated light hadron masses. Understanding their systematic volume dependence may not only help saving computer time in light quark simulations with the Wilson action, but also guide future simulations with dynamical chiral fermions which for a foreseeable time will be restricted to rather small lattices. We analyze data from hybrid Monte Carlo simulations with the N f = 2 Wilson action at two values of the coupling parameter, β = 5.6 (lattice spacing a ≈ 0.08 fm) and β = 5.32144 (a ≈ 0.13 fm). The larger β corresponds to the coupling used previously by SESAM/TχL. The considered hopping parameters κ = 0.1575, 0.158 (at the larger β) and κ = 0.1665 (at the smaller β) correspond to quark masses of 85, 50 and 36% of the strange quark mass, respectively. At each quark mass we study at least three different lattice extents in the range from L = 10 to L = 24 (0.85-2.04 fm). Estimates of autocorrelation times in the stochastic updating process and of the computational cost of every run are given. For each simulated sea quark mass we calculate quark propagators and hadronic correlation functions in order to extract the pion, rho and nucleon masses as well as the pion decay constant and the quark mass from the PCAC relation. We examine to what extent the volume dependence of the masses can be parameterized by simple functions based on M. Lüscher's analytic formula and previous numerical findings by other groups. The applicability of results for the pion and the nucleon from chiral effective theory in the parameter regime covered by our simulations is discussed. Cutoff effects in the PCAC quark mass are found to be under control. Contents 4.4.

Tuning improved anisotropic actions in lattice perturbation theory

Arxiv preprint arXiv:0810.4477, 2008

In recent years, anisotropic lattice actions have seen increasing use in simulations. The 3+1 anisotropic lattice, which has a temporal lattice spacing at that is much less than the spatial lattice spacing as, is obviously very useful in studies of QCD at non-zero temperature, where it ...

Improved nonrelativistic QCD for heavy-quark physics

Physical Review D, 1992

We construct an improved version of nonrelativistic QCD for use in lattice simulations of heavy quark physics, with the goal of reducing systematic errors from all sources to below 10%. We develop power counting rules to assess the importance of the various operators in the action and compute all leading order corrections required by relativity and finite lattice spacing. We discuss radiative corrections to tree level coupling constants, presenting a procedure that effectively resums the largest such corrections to all orders in perturbation theory. Finally, we comment on the size of nonperturbative contributions to the coupling constants. 1

Recent Progress in Lattice QCD

International Journal of Modern Physics A, 2009

In recent years, realistic unquenched QCD simulations have been carried out with various lattice actions. In this report, I explain the progress in theory and algorithms and some of the physics results.