Proton radius from electron-proton scattering and chiral perturbation   theory
  We determine the root-mean-square proton charge radius, $R_{\rm p}$, 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 $R_{\rm p}=0.857(11)$ 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). 
Marko Horbatsch, Eric A. Hessels, Antonio Pineda
nucl-th hep-ph nucl-ex physics.atom-ph