The axial form factor of the nucleon with Padé approximants

Abstract

This work explores the axial-vector form factor of the nucleon, FA(Q2), using Padé approximants as a model-independent alternative to the traditional dipole ansatz. This method allows us to incorporate the a1(1260) resonance to the parametrization of FA(Q2) while also systematically improving the approximation with higher-order Pad´e terms as more precise data becomes available, thereby reducing theoretical uncertainties. We fit data from Lattice QCD simulations and pion electroproduction experiments to extract the mean squared axial radius, ⟨r2A ⟩. The resulting values are ⟨r2A ⟩ = (0.268 ± 0.010) fm2 for the Lattice QCD predictions, ⟨r2A ⟩ = (0.405 ± 0.009) fm2 for the pion electroproduction data and ⟨r2A ⟩ = (0.324 ± 0.006) fm2 for the combined datasets. Finally, we compare our results with determinations from quasielastic neutrino-nucleon scattering cross section νμn → μp experimental data analyses.