QCD with light Wilson quarks on fine lattices (I): first experiences and physics results

TL;DR

This paper reports on advanced lattice QCD simulations with light Wilson quarks at small quark masses, revealing physical effects and confirming chiral perturbation theory predictions up to 500 MeV.

Contribution

First detailed simulations of two-flavour QCD at small quark masses on fine lattices demonstrating physical effects and chiral behavior.

Findings

Physical sea-quark effects are clearly observed.

Lattice effects are small even without O(a) improvement.

Pion mass dependence matches leading-order chiral perturbation theory up to 500 MeV.

Abstract

Recent conceptual, algorithmic and technical advances allow numerical simulations of lattice QCD with Wilson quarks to be performed at significantly smaller quark masses than was possible before. Here we report on simulations of two-flavour QCD at sea-quark masses from slightly above to approximately 1/4 of the strange-quark mass, on lattices with up to 64x32^3 points and spacings from 0.05 to 0.08 fm. Physical sea-quark effects are clearly seen on these lattices, while the lattice effects appear to be quite small, even without O(a) improvement. A striking result is that the dependence of the pion mass on the sea-quark mass is accurately described by leading-order chiral perturbation theory up to meson masses of about 500 MeV.