Nonperturbative tuning of $O(a^2)$ improved staggered fermions

TL;DR

This paper investigates nonperturbative tuning of $O(a^2)$ improved staggered fermion actions to reduce flavor symmetry breaking, finding partial success and suggesting the need for additional action terms.

Contribution

It introduces a nonperturbative tuning method for $O(a^2)$ improved staggered fermions and assesses its effectiveness in reducing flavor symmetry breaking.

Findings

Flavor nondegeneracy can be somewhat reduced

Complete elimination of nondegeneracy not achieved

Additional action terms may be needed

Abstract

We perform a nonperturbative tuning of the coefficients in the $O(a^2)$ improved action for staggered fermions. The mass splitting for the pions of different doubler flavor is used as a measure of the symmetry breaking effects introduced by $O(a^2)$ discretization errors. We find that the flavor nondegeneracy can be somewhat reduced but not eliminated by such a tuning, indicating the need for new terms in the action to reduce the nondegeneracy.