Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks

TL;DR

This paper presents lattice QCD calculations of nucleon electroweak matrix elements using dynamical domain-wall fermions, showing results consistent with experimental data despite small volumes and preliminary statistics.

Contribution

First lattice QCD study using dynamical domain-wall fermions to compute nucleon structure, demonstrating agreement with experimental ratios and mild quark mass dependence.

Findings

Ratios g_A/g_V and <x>_{u-d}/<x>_{Delta u - Delta d} agree with experiment

Results show mild quark mass dependence

Small d_1 structure function moment observed

Abstract

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm)^3. Despite the small volume, the ratio of the isovector vector and axial charges g_A/g_V and that of structure function moments <x>_{u-d}/<x>_{Delta u - Delta d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm)^3. Even with preliminary statistics of 25-30 gauge configurations, the ratios g_A/g_V and <x>_{u-d}/<x>_{Delta u - Delta d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d_1, though yet to be renormalized, appears small in both sets.