Coulomb Corrections to Elastic Electron-Proton Scattering and the Proton Charge Radius

Abstract

Recent values of the proton charge radius derived from the Lamb shift in electronic hydrogen tend to be larger than those from electron scattering. Therefore low-momentum-transfer scattering data from different groups and laboratories have been reanalyzed with Coulomb and recoil corrections included. This was done by calculating at each scattering angle and scattering energy the corresponding correction obtained from a partial wave program which includes recoil approximately. Corrections due to magnetic scattering were also made before the rms-radius was determined by a fit which allows free normalization for each experiment. It is shown that an analysis of electron scattering data including Coulomb corrections lowers the $χ^2$ of the fit and increases the proton radius by about (0.008 - 0.013) fm depending on the fit strategy. A value of r_p = 0.880 (15) fm is obtained which is in good agreement with the one extracted from Lamb shift measurements.