Nucleon Vector and Axial-Vector Form Factors

Abstract

We present a status report on the calculation of the isovector axial-vector and vector form factors of the nucleon using (i) eight ensembles of N_f = 2 + 1 + 1 HISQ fermions at lattice spacings a = 0.12, 0.09, and 0.06 fm and three values of light quark masses corresponding to M_\pi = 310, 220, 130 MeV generated by the MILC collaboration and (ii) four ensembles of clover fermions generated by the JLAB/W&M collaboration. In both cases, the clover action is used for valence quarks. Analysis of the Q^2 dependence of the form factors is carried out using the z−expansion and the dipole ansatz. The results for the charge radii and dipole masses are compared and found to be consistent between the two fit ansatz and between the two lattice formulations.