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 pi pi -> N (N) over bar data. Using representative data sets we find r(E)(p) = 0.870 +/- 0.023 +/- 0.012 fm using just proton scattering data; r(E)(p) = 0.880(-0.020)(+0.017) +/- 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.