Finite-size scaling in nucleon axial charge from 2+1-flavor DWF lattice QCD

for RBC and UKQCD Collaborations We report the current status of the on-going lattice-QCD calculations of nucleon isovector ax-ial charge, gA, using the RBC/UKQCD 2+1-flavor dynamical domain-wall fermion ensembles at lattice cutoff of about a−1 = 1.4 GeV in a spatial volume (L = 4.6fm)3. The result from the ensemble with mpi = 250 MeV pion mass, corresponding to the finite-size scaling parameter mpiL ∼ 5.8, agrees well with an earlier result at a−1 = 1.7 GeV, L = 2.8 fm, and mpi = 420 MeV, with similar mpiL. This suggests the systematic error from excited-state contamination is small in both ensembles and about 10- % deficit in gA we are observing is likely a finite-size effect that scales with mpiL. We also report the result from the lighter, mpi = 170 MeV ensemble