Nucleon scalar and tensor couplings from lattice QCD at the physical points

Abstract

We present results for the axial, scalar and tensor isovector-couplings (gA, gS and gT) of the nucleon obtained from 2+1 flavor QCD with the physical light quark masses (Mπ = 135 MeV). Our calculations are performed at a single lattice spacing of 0.085 fm, but with two large volumes of (10.9 fm)4 and (5.5 fm)4. The configurations are generated by the PACS Collaboration with nonperturbatively 𝒪(a) improved Wilson quark action and Iwasaki gauge action. The result of gA is a good indicator for determination of gS and gT with respect to accuracy and precision. Our result of gA well reproduces the experimental value within a statistical error of less than 2%. As for gS and gT, we compute the renormalization constants at the scale of 2 GeV in the ̅M̅S scheme through the RI/SMOM(γμ) intermediate scheme, and then obtain gS = 0.927(83)stat(22)syst and gT = 1.036(6)stat(20)syst.