A Field-Theoretic Parametrization of Low-Energy Nucleon Form Factors

TL;DR

This paper introduces a Lorentz covariant, chirally symmetric field-theoretic parametrization for nucleon electromagnetic form factors below 600 MeV, effectively fitting experimental data and enabling advanced nuclear structure studies.

Contribution

It presents a novel effective field theory parametrization based on vector meson dominance and derivative expansion, accurately fitting nucleon form factors up to 600 MeV.

Findings

Successfully fits nucleon form factor data within a few percent up to 600 MeV

Demonstrates the importance of vector meson dominance in the parametrization

Enables study of two-body electromagnetic exchange currents in nuclei

Abstract

A field-theoretic parametrization is proposed for nucleon electromagnetic form factors at momentum transfer less than 600 MeV. The parametrization is part of a larger effective field theory lagrangian that is Lorentz covariant and chirally symmetric, and that has been used to successfully describe bulk and single-particle properties of medium to heavy mass nuclei. The parametrization is based on vector meson dominance and a derivative expansion of nucleon couplings to the electromagnetic fields. At lowest order in the expansion, it is possible to fit all four parameters to modern data on the rms radii of the nucleon form factors. At next-to-leading order it is possible to fit the form factors to within a few percent up to momentum transfers of 600 MeV. The vector meson dominance contributions are crucial in this fit, since a simple expansion in powers of momentum transfer would require many, many terms to achieve comparable accuracy. The ability to fit single-nucleon form factors up to 600 MeV momentum transfer makes possible the study of two-body electromagnetic exchange currents within this effective field theory framework.