We perform a precise calculation of physical quantities related to the axial structure of the nucleon using 2+1 flavor lattice QCD gauge configuration (PACS10 configuration) generated at the physical point with lattice volume larger than (10 fm)4 by the PACS Collaboration. The nucleon matrix element of the axial-vector current has two types of the nucleon form factors, the axial-vector (FA) form factor and the induced pseudoscalar (FP) form factor. Recently, lattice QCD simulations have succeeded in reproducing the experimental value of the axial-vector coupling, gA, determined from FA(q2) at zero momentum transfer q2=0, at a percent level of statistical accuracy. However, the FP form factor so far has not reproduced the experimental values well due to strong πN excited-state contamination. Therefore, we propose a simple subtraction method for removing the so-called leading πN-state contribution. This method succeeds in reproducing the values obtained by two experiments of muon capture on the proton and pion electroproduction for FP(q2). The novel approach can also be applied to determine the pseudoscalar (GP) form factor from the nucleon pseudoscalar matrix element with the help of the axial Ward-Takahashi identity. The resulting form factors, FP(q2) and GP(q2), are in good agreement with the prediction of the pion-pole dominance model. In the new analysis, the induced pseudoscalar coupling gP* and the pion-nucleon coupling gπNN can be evaluated with a few percent accuracy including systematic uncertainties using existing data calculated at two lattice spacings.
Aoki et al. (2025) studied this question.