Model-independent extraction of the proton charge radius from electron scattering

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 ππ→NN̄ data. Using representative data sets we find rEᵖ=0.870±0.023±0.012 fm using just proton scattering data; rEᵖ=0.880_-0.020+0.017±0.007 fm adding neutron data; and rEᵖ=0.871±0.009±0.002±0.002 fm adding ππ data. The analysis can be readily extended to other nucleon form factors and derived observables.