Proton radius from electron-proton scattering and chiral perturbation theory

Abstract

We determine the root-mean-square proton charge radius, $R_{\mathrm{p}}$, from a fit to low-$Q^2$ electron-proton elastic scattering cross section data with the higher moments fixed (within uncertainties) to the values predicted by chiral perturbation theory. We obtain $R_{\mathrm{p}}=0.857(11)$ fm. This number falls between the value obtained from muonic hydrogen analyses and the CODATA value (based upon atomic hydrogen spectroscopy and electron-proton scattering determinations).

Comments: Updated to match published version, with minor numerical changes, and added and corrected references. Conclusions unchanged