Nucleon Isovector Axial Form Factors

We present results for the isovector axial vector form factors obtained using thirteen 2 + 1 + 1-flavor highly improved staggered quark (HISQ) ensembles generated by the MILC collaboration. The calculation of nucleon two- and three-point correlation functions has been done using Wilson-clover fermions. In the analysis of these data, we quantify the sensitivity of the results to strategies used for removing excited state contamination and invoke the partially conserved axial current relation between the form factors to choose between them. Our data driven analysis includes removing contributions from multihadron $Nπ$ states that make significant contributions. Our final results are $g_A$ = 1.292(53)_stat(24)_sys for the axial charge; $g_S$ = 1.085(50)_stat(103)_sys and $g_T$ = 0.991(21)_stat(10)_sys for the scalar and tensor charges; $\langle{r^2_A}\rangle$ = 0.439(56)_stat(34)_sys fm² for the mean squared axial charge radius, $g^*_P$ = 9.03(47)_stat(42)_sys for the induced pseudoscalar charge; and $g_{πNN}$ = 14.14(81)_stat(85)_sys for the pion-nucleon coupling. We also provide a parametrization of the axial form factor $G_A(Q^2)$ over the range 0 ≤ $Q^2$ ≤ 1 GeV² for use in phenomenology and a comparison with other lattice determinations. We find that the various lattice data agree within 10% but are significantly different from the extraction of $G_A(Q^2)$ from the $ν$-deuterium scattering data.. Authors: Jang, Yong-Chull [Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States)]; Gupta, Rajan [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000317843058); Bhattacharya, Tanmoy [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:000000021060652X); Yoon, Boram [NVIDIA Corporation, Santa Clara, CA (United States)]; Lin, Huey-Wen [Michigan State Univ., East Lansing, MI (United States)]. DOE Contract: 89233218CNA000001; AC02-05CH11231; AC05-00OR22725; AC52-06NA25396. Subjects: 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; axial vector, form factors, lattice QCD, nuclear charges