Nucleon axial charge in 2+1 flavor dynamical lattice QCD with domain wall fermions

TL;DR

This study computes the nucleon axial charge using 2+1 flavor domain wall fermions in lattice QCD, analyzing finite volume effects and scaling behavior to estimate the physical value at the pion mass of 135 MeV.

Contribution

It provides the first detailed analysis of finite volume effects on g_A with 2+1 flavor dynamical fermions and introduces a scaling method to correct for these effects.

Findings

Finite volume effects are significant at m_π=330 MeV.

g_A scales with m_π L, enabling finite-volume correction.

Estimated g_A at physical pion mass is 1.20(6)(4).

Abstract

We present results for the nucleon axial charge g_A at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16^3x32 and 24^3x64lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_\pi is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m_\pi= 330 MeV. We also find that g_A exhibits a scaling with the single variable m_\pi L which can also be seen in previous two-flavor domain wall and Wilson fermion calculati ons. Using this scaling to eliminate the finite-volume effect, we obtain g_A = 1.20(6)(4) at the physical pion mass, m_\pi = 135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V\ge (2.4 fm)^3. We argue this is a dynamical quark effect.