Nucleon form factors in N f = 2 + 1 lattice QCD at the physical point: Finite lattice spacing effect on the root-mean-square radii

We present results for the nucleon form factors: electric ( G E ), magnetic ( G M ), axial ( F A ), induced pseudoscalar ( F P ), and pseudoscalar ( G P ) form factors, using the second PACS10 ensemble that is one of three sets of 2 + 1 flavor lattice QCD configurations at physical quark masses in large spatial volumes [exceeding ( 10 fm ) 3 ]. The second PACS10 gauge configurations are generated by the PACS Collaboration with the six stout-smeared O ( a ) improved Wilson quark action and Iwasaki gauge action at the second gauge coupling β = 2.00 corresponding to the lattice spacing of a = 0.063 fm . We determine the isovector electric, magnetic and axial radii, and magnetic moment from the corresponding form factors, as well as the axial-vector coupling g A . Combining our previous results for the coarser lattice spacing [E. Shintani , ; ], the finite lattice spacing effects on the isovector radii, magnetic moment, and axial-vector coupling are investigated using the difference between the two results. It was found that the effect on g A is kept smaller than the statistical error of 2% while the effect on the isovector radii was observed as a possible discretization error of about 10%, regardless of the channel. We also report the partially conserved axial-vector current relation using a set of nucleon three-point correlation functions in order to verify the effect by O ( a ) improvement of the axial-vector current.