Topological susceptibility with three flavors of staggered quarks

TL;DR

This study tests the validity of the staggered-fermion fourth-root trick by examining topological susceptibility suppression in QCD with 2+1 flavors, using improved techniques and chiral perturbation theory for accurate results.

Contribution

It provides new lattice QCD results on topological susceptibility with 2+1 flavors, incorporating taste-breaking effects and continuum extrapolation, supporting the validity of the staggered fermion approach.

Findings

Results agree with chiral perturbation theory predictions.

Taste-breaking effects are effectively modeled, reducing scaling violations.

Continuum extrapolation yields consistent susceptibility values.

Abstract

As one test of the validity of the staggered-fermion fourth-root determinant trick, we examine the suppression of the topological susceptibility of the QCD vacuum in the limit of small quark mass. The suppression is sensitive to the number of light sea quark flavors. Our study is done in the presence of 2+1 flavors of dynamical quarks in the improved staggered fermion formulation. Variance-reduction techniques provide better control of statistical errors. New results from staggered chiral perturbation theory account for taste-breaking effects in the low-quark mass behavior of the susceptibility, thereby reducing scaling violations from this source. Measurements over a range of quark masses at two lattice spacings permit a rough continuum extrapolation to remove the remaining lattice artifacts. The results are consistent with chiral perturbation theory with the correct flavor counting.