Reweighting towards the chiral limit

TL;DR

The paper introduces a reweighting method for dynamical lattice QCD simulations at small quark masses, enabling exploration of the epsilon-regime without direct simulation difficulties.

Contribution

It presents a novel reweighting technique using stochastic weight factors, determinant breakup, and low mode projection to efficiently reach very small quark masses in lattice QCD.

Findings

Successfully reweighted from 20MeV to 5MeV quark masses

Achieved moderate fluctuations in weight factors on smeared ensembles

Calculated the low energy constant F in the epsilon-regime

Abstract

We propose to perform fully dynamical simulations at small quark masses by reweighting in the quark mass. This approach avoids some of the technical difficulties associated with direct simulations at very small quark masses. We calculate the weight factors stochastically, using determinant breakup and low mode projection to reduce the statistical fluctuations. We find that the weight factors fluctuate only moderately on nHYP smeared dynamical Wilson-clover ensembles, and we could successfully reweight 16^4, (1.85fm)^4 volume configurations from m_q = 20MeV to m_q = 5MeV quark masses, reaching the epsilon-regime. We illustrate the strength of the method by calculating the low energy constant F from the epsilon-regime pseudo-scalar correlator.