Nucleon axial charge in 2+1-flavor dynamical DWF lattice QCD

The current status of some nucleon isovector observables, the vector charge, (g_V), axial charge, (g_A), quark momentum fraction, (langle x rangle_{u-d}), and quark helicity fraction, (langle x rangle_{Delta u - Delta d}), calculated using recent RBC/UKQCD 2+1-flavor dynamical domain-wall fermions (DWF) lattice QCD ensembles are reported: with Iwasaki gauge action at inverse lattice spacing, (a^{-1}), of about 1.7 GeV, linear lattice extent, (L), of about 2.7 fm, pion mass, (m_pi), of about 420 and 330 MeV, and with Iwasaki(times)DSDR gauge action at (a^{-1}) of about 1.4 GeV, (L) of about 4.6 fm, and (m_pi) of about 250 and 170 MeV. The calculations have been refined with enhanced statistics, in particular through successful application of the all-mode-averaging (AMA) technique for the 170- and 330-MeV ensembles. As a result, the precision agreement seen in the charge ratio, (g_A/g_V), for 420-MeV and 250-MeV ensembles that share the finite-size scaling parameter (m_pi L) of about 5.8 is more significant with new values of 1.17(2) and 1.18(4) respectively. We also studied the dependence on the source-sink separation in the lightest ensemble of 170-MeV, by comparing the cases with the separation of about 1.0 and 1.3 fm and did not see any dependence: contamination from the excited states are well under control in our choice of source and sink smearing. The axial charge, (g_A) and the ratio, (g_A/g_V), shows a long-range autocorrelation that extends the entire range of configurations that were so far analyzed, almost 700 hybrid Molecular Dynamics time, in the lightest ensemble of (m_pi=170) MeV. The other observables do not show any autocorrelation with the interval of 16 trajectories.