Scaling studies of QCD with the dynamical HISQ action

TL;DR

This study compares the lattice spacing dependence of physical quantities using the HISQ and asqtad fermion actions in lattice QCD, demonstrating that HISQ exhibits significantly reduced lattice artifacts at comparable spacings.

Contribution

It provides a detailed analysis of the scaling behavior of the HISQ action and compares it to the asqtad action, highlighting improvements in lattice artifact reduction.

Findings

HISQ has smaller lattice artifacts than asqtad at the same lattice spacings.

Lattice spacing dependence of hadron masses and decay constants is systematically studied.

Different methods for setting the lattice scale are compared and analyzed.

Abstract

We study the lattice spacing dependence, or scaling, of physical quantities using the highly improved staggered quark (HISQ) action introduced by the HPQCD/UKQCD collaboration, comparing our results to similar simulations with the asqtad fermion action. Results are based on calculations with lattice spacings approximately 0.15, 0.12 and 0.09 fm, using four flavors of dynamical HISQ quarks. The strange and charm quark masses are near their physical values, and the light-quark mass is set to 0.2 times the strange-quark mass. We look at the lattice spacing dependence of hadron masses, pseudoscalar meson decay constants, and the topological susceptibility. In addition to the commonly used determination of the lattice spacing through the static quark potential, we examine a determination proposed by the HPQCD collaboration that uses the decay constant of a fictitious "unmixed s bar s" pseudoscalar meson. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses.