The role of the double pole in lattice QCD with mixed actions

TL;DR

This paper studies how using different discretizations for valence and sea quarks in lattice QCD introduces a double pole in flavor-neutral meson propagators, affecting scaling violations and observable sensitivities.

Contribution

It demonstrates the presence of a double pole in flavor-neutral Goldstone meson propagators in mixed-action lattice QCD and analyzes its impact on scaling violations and observables.

Findings

Double pole exists even when charged mesons have equal masses.

Double-pole effects on certain observables may be small in practice.

Scaling violations due to the double pole are theoretically significant.

Abstract

We investigate effects resulting from the use of different discretizations for the valence and the sea quarks in lattice QCD, considering Wilson and/or Ginsparg-Wilson fermions. We assume that such effects appear through scaling violations that can be studied using effective lagrangian techniques. We show that a double pole is present in flavor-neutral Goldstone meson propagators,even if the charged Goldstone mesons made out of valence quarks and those made out of sea quarks have equal masses. We then consider some observables known to be anomalously sensitive to the presence of a double pole. For these observables, we find that the double-pole enhanced scaling violations may turn out to be rather small in practice.