Electromagnetic form factors of the nucleon in effective field theory

TL;DR

This paper computes the nucleon's electromagnetic form factors using a Lorentz-invariant effective field theory including mesons and resonances, applying a systematic power counting scheme to compare with experimental data.

Contribution

It introduces a third-order chiral effective field theory with explicit meson and resonance degrees of freedom, using the extended on-mass-shell scheme for systematic calculations.

Findings

Results agree with experimental form factor data

Pion-mass dependence of form factors analyzed

Comparison with previous chiral perturbation theory results

Abstract

We calculate the electromagnetic form factors of the nucleon to third chiral order in manifestly Lorentz-invariant effective field theory. The rho and omega mesons as well as the Delta(1232) resonance are included as explicit dynamical degrees of freedom. To obtain a self-consistent theory with respect to constraints we consider the proper relations among the couplings of the effective Lagrangian. For the purpose of generating a systematic power counting, the extended on-mass-shell renormalization scheme is applied in combination with the small-scale expansion. The results for the electric and magnetic Sachs form factors are analyzed in terms of experimental data and compared to previous findings in the framework of chiral perturbation theory. The pion-mass dependence of the form factors is briefly discussed.