Probing the chiral regime of Nf=2 QCD with mixed actions

TL;DR

This study explores the chiral properties of Nf=2 QCD using a mixed action approach with overlap valence quarks and Wilson sea quarks, comparing results to Chiral Perturbation Theory to test the framework's consistency.

Contribution

First application of mixed action setup with overlap valence and Wilson sea quarks to probe chiral regime and compare to NLO ChPT predictions.

Findings

Agreement with NLO ChPT in the mixed regime.

Two determinations of the chiral condensate.

Insights into NLO low-energy couplings.

Abstract

We report on our first experiences with a mixed action setup with overlap valence quarks and non-perturbatively O(a) improved Wilson sea quarks. For the latter we employ CLS Nf=2 configurations with light sea quark masses at small lattice spacings. Exact chiral symmetry allows to consider very light valence quarks and explore the matching to (partially quenched) Chiral Perturbation Theory (ChPT) in a mixed epsilon/p-regime. We compute the topological susceptibility and the low-lying spectrum of the massless Neuberger-Dirac operator for three values of the sea quark mass, and compare the sea quark mass dependence to NLO ChPT in the mixed regime. This provides two different determinations of the chiral condensate, as well as information about some NLO low-energy couplings. Our results allow to test the consistency of the mixed-regime approach to ChPT, as well as of the mixed action framework.