Model independent extraction of the proton charge radius from electron scattering

TL;DR

This paper presents a model-independent method combining analyticity constraints with electron-proton scattering data to accurately determine the proton charge radius, including effects of additional scattering data.

Contribution

It introduces a systematic, model-independent analysis procedure for extracting the proton charge radius from scattering data, incorporating various datasets and constraints.

Findings

Proton charge radius r_E^p ≈ 0.87 fm from proton data

Including neutron data slightly increases r_E^p to about 0.88 fm

Adding pion-pion data yields a radius around 0.87 fm

Abstract

Constraints from analyticity are combined with experimental electron-proton scattering data to determine the proton charge radius. In contrast to previous determinations, we provide a systematic procedure for analyzing arbitrary data without model-dependent assumptions on the form factor shape. We also investigate the impact of including electron-neutron scattering data, and $\pi\pi\to N\bar{N}$ data. Using representative datasets we find r_E^p=0.870 +/- 0.023 +/- 0.012 fm using just proton scattering data; r_E^p=0.880^{+0.017}_{-0.020} +/- 0.007 fm adding neutron data; and r_E^p=0.871 +/- 0.009 +/- 0.002 +/- 0.002 fm adding $\pi\pi$ data. The analysis can be readily extended to other nucleon form factors and derived observables.