Chiral behavior of pseudo-Goldstone boson masses and decay constants in 2+1 flavor QCD

TL;DR

This paper investigates the chiral behavior of pseudo-Goldstone boson masses and decay constants in 2+1 flavor QCD, highlighting the importance of including O(a^2) unitarity violations to explain observed discrepancies.

Contribution

It demonstrates that incorporating O(a^2) unitarity violations into chiral perturbation theory explains the chiral behavior in mixed-action lattice QCD simulations.

Findings

Inclusion of O(a^2) unitarity violations resolves discrepancies in chiral behavior.

Discrepancies are consistent with observed unitarity violations in scalar meson propagators.

Mixed-action simulations require extended chiral perturbation theory for accurate description.

Abstract

We present preliminary results for the chiral behavior of charged pseudo-Goldstone-boson masses and decay constants. These are obtained in simulations with N_f=2+1 flavors of tree-level, O(a)-improved Wilson sea quarks. In these simulations, mesons are composed of either valence quarks discretized in the same way as the sea quarks (unitary simulations) or of overlap valence quarks (mixed-action simulations). We find that the chiral behavior of the pseudoscalar meson masses in the mixed-action calculations cannot be explained with continuum, partially-quenched chiral perturbation theory. We show that the inclusion of O(a^2) unitarity violations in the chiral expansion resolves this discrepancy and that the size of the unitarity violations required are consistent with those which we observe in the zero-momentum, scalar-isotriplet-meson propagator.