Nucleon mass and isovector couplings in 2+1-flavor dynamical domain-wall lattice QCD near physical mass

TL;DR

This paper presents lattice QCD calculations of nucleon properties near the physical pion mass, including mass, isovector charges, and couplings, providing insights into nucleon structure with high precision.

Contribution

The study provides new lattice QCD results for nucleon observables using 2+1-flavor dynamical domain-wall fermions close to physical masses, with improved accuracy and consistency.

Findings

Nucleon mass extrapolates to 0.950 GeV at physical point.

Isovector vector charge approaches unity in the chiral limit.

Tensor coupling extrapolates to 1.04 in MS-bar scheme at physical point.

Abstract

We report nucleon mass, isovector vector and axial-vector charges, and tensor and scalar couplings, calculated using two recent 2+1-flavor dynamical domain-wall fermions lattice-QCD ensembles generated jointly by the RIKEN-BNL-Columbia and UKQCD collaborations. These ensembles were generated with Iwasaki $\times$ dislocation-suppressing-determinant-ratio gauge action at inverse lattice spacing of 1.378(7) GeV and pion mass values of 249.4(3) and 172.3(3) MeV. The nucleon mass extrapolates to a value $m_N = 0.950(5)$ GeV at physical point. The isovector vector charge renormalizes to unity in the chiral limit, narrowly constraining excited-state contamination in the calculation. The ratio of the isovector axial-vector to vector charges shows a deficit of about ten percent. The tensor coupling no longer depends on mass and extrapolates to 1.04(5) in $\overline {\rm MS}$ 2-GeV renormalization at physical point, in a good agreement with the value obtained at the lightest mass in our previous calculations and other calculations that followed. The scalar charge, though noisier, does not show mass dependence and is in agreement with other calculations.