We consider the chiral Lagrangian with nucleon, isobar, and pion degrees of freedom. The baryon masses and the axial-vector form factor of the nucleon are derived at the one-loop level. We explore the impact of using on-shell baryon masses in the loop expressions. As compared to results from conventional chiral perturbation theory we find significant differences. An application to QCD lattice data is presented. We perform a global fit to the available lattice data sets for the baryon masses and the nucleon axial-vector form factor, and determine the low-energy constants relevant at N3LO for the baryon masses and at N2LO for the form factor. Partial finite-volume effects are considered. We point out that the use of on-shell masses in the loops results in non-analytic behavior of the baryon masses and the form factor as function of the pion mass, which becomes prominent for larger lattice volumes than presently used.
@article{arxiv.2003.10158,
title = {On the axial-vector form factor of the nucleon and chiral symmetry},
author = {Matthias F. M. Lutz and Ulrich Sauerwein and Rob G. E. Timmermans},
journal= {arXiv preprint arXiv:2003.10158},
year = {2020}
}