Evaluation of the strength of electron-proton scattering data for determining the proton charge radius

Precisely measured electron-proton elastic scattering cross sections [Phys. Rev. Lett. 105, 242001 (2010)] are reanalyzed to evaluate their strength for determining the rms charge radius (RE) of the proton. More than half of the cross sections at lowest Q² are fit using two single-parameter form-factor models, with the first based on a dipole parametrization, and the second on a linear fit to a conformal-mapping variable. These low-Q² fits extrapolate the slope of the form factor to Q²=0 and determine RE values of approximately 0.84 and 0.89 fm, respectively. Fits spanning all Q², in which the single constants are replaced with cubic splines at larger Q², lead to similar results for RE. We conclude that the scattering data are consistent with RE ranging from at least 0.84 to 0.89 fm, and therefore is consistent with both of the discrepant determinations of RE made using muonic and electronic hydrogen-atom spectroscopy.