Nucleon isovector charges from physical mass domain-wall QCD

TL;DR

This paper calculates nucleon isovector vector and axialvector charges using physical mass domain-wall QCD, analyzing systematic errors and comparing results with experimental data.

Contribution

It provides the first detailed analysis of nucleon charges from 2+1-flavor DWF at physical mass with systematic error assessment.

Findings

Vector charge systematic error consistent with $O(a^2)$ discretization.

Axialvector charge shows a significant deficit compared to experiments.

Statistical errors are about 1% or less.

Abstract

Systematics in nucleon isovector vector, $g_V$, and axialvector, $g_A$, charges calculated on a 2+1-flavor dynamical domain-wall-fermions (DWF) ensemble at physical mass jointly generated by RIKEN-BNL-Columbia (RBC) and UKQCD Collaborations with lattice cut off of 1.730(4) GeV, are analyzed. Both are calculated with about a percent or less statistical errors. A few standard-deviation systematics seen in vector charge is consistent with possible $O(a^2)$ discretization error through small excited-state contamination. Axialvector charge is found with three to nine standard-deviation systematic deficit, compared with experiments, depending on calculation methods.