Systematics analyses on nucleon isovector observables in 2+1-flavor dynamical domain-wall lattice QCD near physical mass

TL;DR

This paper investigates systematic uncertainties in nucleon isovector observables using 2+1-flavor domain-wall lattice QCD near physical pion mass, highlighting error growth in axial charge and transversity related to autocorrelation effects.

Contribution

It provides a detailed analysis of systematic errors and autocorrelation effects in key nucleon observables computed with domain-wall fermions near physical mass.

Findings

No autocorrelation in vector charge and quark momentum fractions.

Error growth in axial charge and transversity linked to autocorrelation times.

Errors in axial charge increase with larger block sizes, indicating autocorrelation issues.

Abstract

Analyses on possible systematics in some isovector nucleon observables in the RBC+UKQCD 2+1-flavor dynamical domain-wall fermion (DWF) lattice-QCD are presented. The vector charge, axial charge, quark momentum and helicity fractions, and transversity are discussed using mainly the Iwasaki\(\times\)DSDR ensemble at pion mass of 170 MeV. No autocorrelation issue is observed in the vector charge and quark momentum and helicity fractions. Blocked Jack-knife analyses expose significant growth of estimated error for the axial charge with increasing block sizes that are similar to or larger than the known autocorrelation time of the gauge-field topological charge. Similar growth is seen in the transversity. These two observables, however, do not seem correlated with the topological charge.