Light Quark Mass Reweighting

TL;DR

This paper evaluates the effectiveness of light quark mass reweighting in lattice QCD, demonstrating its potential to accurately estimate results for different quark masses from a single ensemble despite large fluctuations.

Contribution

It systematically studies the feasibility of reweighting between significantly different light quark masses in lattice QCD using domain wall fermions.

Findings

Reweighted results agree with direct calculations within statistical errors.

Reweighting from heavier to lighter quark masses is more effective.

Despite large fluctuations, reweighting provides consistent physical observables.

Abstract

We present a systematic study of the effectiveness of light quark mass reweighting. This method allows a single lattice QCD ensemble, generated with a specific value of the dynamical light quark mass, to be used to determine results for other, nearby light dynamical quark masses. We study two gauge field ensembles generated with 2+1 flavors of dynamical domain wall fermions with light quark masses m_l=0.02 (m_\pi=620 MeV) and m_l=0.01 (m_\pi=420 MeV). We reweight each ensemble to determine results which could be computed directly from the other and check the consistency of the reweighted results with the direct results. The large difference between the 0.02 and 0.01 light quark masses suggests that this is an aggressive application of reweighting as can be seen from fluctuations in the magnitude of the reweighting factor by four orders of magnitude. Never-the-less, a comparison of the reweighed topological charge, average plaquette, residual mass, pion mass, pion decay constant, and scalar correlator between these two ensembles shows agreement well described by the statistical errors. The issues of the effective number of configurations and finite sample size bias are discussed. An examination of the topological charge distribution implies that it is more favorable to reweight from heavier mass to lighter quark mass.