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

¹ Department of Physics, Tohoku University, 980-8578, Sendai, Japan
² RIKEN Center for Computational Science, 650-0047, Kobe, Japan
³ Core of Research for the Energetic Universe, Graduate School of Advanced Science and Engineering, Hiroshima University, 739-8526, Higashi-Hiroshima, Japan
⁴ Center for Computational Sciences, University of Tsukuba, 305-8577, Tsukuba, Japan
⁵ Faculty of pure and Applied Sciences, University of Tsukuba, 305-8571, Tsukuba, Japan

^* e-mail: tsuji@nucl.phys.tohoku.ac.jp

Published online: 22 December 2022

Abstract

We present results for the axial, scalar and tensor isovector-couplings (g_A, g_S and g_T) of the nucleon obtained from 2+1 flavor QCD with the physical light quark masses (M_π = 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 g_S and g_T with respect to accuracy and precision. Our result of g_A well reproduces the experimental value within a statistical error of less than 2%. As for g_S and g_T, 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 g_S = 0.927(83)_stat(22)_syst and g_T = 1.036(6)_stat(20)_syst.