Further Improvements to Staggered Quarks

TL;DR

This paper presents further enhancements to the staggered quark action in lattice QCD, reducing taste-changing errors through additional link smearing, thereby improving the accuracy of simulations with three light dynamical quarks.

Contribution

The paper introduces additional link smearing techniques that halve taste-changing errors while maintaining an $a^2$-improved quark action, advancing lattice QCD simulations.

Findings

Additional smearing reduces taste-changing errors by a factor of two.

Perturbative calculations explain taste-breaking effects.

Highly improved action facilitates unquenching techniques.

Abstract

The improved staggered quark action has enabled breakthrough calculations of QCD with three light dynamical quarks. The largest remaining $a^2$ scaling violations come from "taste-changing" interactions, which are significantly reduced over naive quarks because of carefully chosen smearing of the gauge links. Here we examine further improvements to the quark action and show that additional smearing of the links can reduce the taste-changing errors by another factor of two, whilst retaining a fully $a^2$-improved action. The taste-changing errors can be understood within a perturbative calculation of the four-quark operators that appear at one-loop. We also discuss unquenching techniques with such a highly improved action.