Accurate nucleon electromagnetic form factors from dispersively improved chiral effective field theory

TL;DR

This paper develops a theoretical model combining chiral effective field theory and dispersion analysis to accurately describe nucleon electromagnetic form factors, achieving excellent agreement with experimental data and enabling precise proton radius extraction.

Contribution

It introduces a dispersively improved chiral effective field theory approach for nucleon form factors, incorporating spectral functions and effective poles with uncertainty estimates.

Findings

Achieves excellent fit to proton and neutron form factor data up to Q^2 ~ 1 GeV^2

Provides a model with proper analyticity and uncertainty quantification

Enables improved low-Q^2 form factor studies and proton radius determination

Abstract

We present a theoretical parametrization of the nucleon electromagnetic form factors (FFs) based on a combination of chiral effective field theory and dispersion analysis. The isovector spectral functions on the two-pion cut are computed using elastic unitarity, chiral pion-nucleon amplitudes, and timelike pion FF data. Higher-mass isovector and isoscalar t-channel states are described by effective poles, whose strength is fixed by sum rules (charges, radii). Excellent agreement with the spacelike proton and neutron FF data is achieved up to Q^2 \sim 1 GeV^2. Our parametrization provides proper analyticity and theoretical uncertainty estimates and can be used for low-Q^2 FF studies and proton radius extraction.