Improvement of the pion spectrum with HYP-smeared staggered fermions

TL;DR

This paper demonstrates that HYP smearing significantly reduces taste-symmetry breaking in staggered fermions, improving the pion spectrum accuracy in lattice QCD simulations.

Contribution

It provides a comprehensive comparison of HYP-smeared and unimproved staggered fermions, including unquenched lattices, showing the effectiveness of HYP smearing in reducing discretization effects.

Findings

Taste breaking is substantially reduced by HYP smearing.

HYP smearing brings discretization effects to expected levels for any fermion type.

Complete comparison of all pion tastes with improved statistics.

Abstract

We extend our previous study of taste-symmetry breaking using HYP-smeared staggered fermions in two ways. First, we improve the statistics of a comparison of unimproved and HYP-smeared staggered fermions on quenched lattices with $a\approx 0.1 $fm. This allows us to obtain a signal for all pion tastes, rather than just a subset, and thus to make a complete comparison. In addition, it allows us to differentiate between wall and local sources. Second, we compare HYP-smeared valence quarks to asqtad valence quarks on 2+1 flavor unquenched MILC lattices. We find that taste breaking is substantially reduced by HYP-smearing, bringing the size of this discretization effect (which is the dominant such effect with staggered fermions) down to the size expected generically for any fermion type.