Low energy chiral constants from epsilon-regime simulations with improved Wilson fermions

TL;DR

This paper reports a lattice QCD study in the epsilon regime using improved Wilson fermions to determine low energy constants of the chiral Lagrangian, achieving results consistent with theoretical expectations.

Contribution

It introduces a novel approach combining improved Wilson fermions and reweighting to accurately extract low energy constants in the epsilon regime.

Findings

F=90(4) MeV in MS-bar scheme

Sigma^(1/3)=248(6) MeV in MS-bar scheme

Data well fitted with NLO chiral perturbation theory

Abstract

We present a lattice QCD calculation of the low energy constants of the leading order chiral Lagrangian. In these simulations the epsilon regime is reached by using tree-level improved nHYP Wilson fermions combined with reweighting in the quark mass. We analyze two point functions on two ensembles with lattices of size (1.85fm)^4 and (2.8fm)^4, and at several quark mass values between 4 and 20 MeV. The data are well fitted with next-to-leading order chiral perturbative formulae and predict F=90(4)MeV and Sigma^(1/3)=248(6)MeV in the MS-bar scheme at 2 GeV.