We report on lattice QCD calculations of the nucleon isovector axial, scalar, and tensor charges. Our calculations are performed on two 2+1-flavor ensembles generated using a 2-HEX-smeared Wilson-clover action at the physical pion mass and lattice spacings a≈0.116 and 0.093 fm. We use a wide range of source-sink separations - eight values ranging from roughly 0.4 to 1.4 fm on the coarse ensemble and three values from 0.9 to 1.5 fm on the fine ensemble - which allows us to perform an extensive study of excited-state effects using different analysis and fit strategies. To determine the renormalization factors, we use the nonperturbative Rome-Southampton approach and compare RI′-MOM and RI-SMOM intermediate schemes to estimate the systematic uncertainties. Our final results are computed in the MS scheme at scale 2 GeV. The tensor and axial charges have uncertainties of roughly 4%, gT=0.972(41) and gA=1.265(49). The resulting scalar charge, gS=0.927(303), has a much larger uncertainty due to a stronger dependence on the choice of intermediate renormalization scheme and on the lattice spacing.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)