The short distance behavior of the proton electromagnetic structure

The charge density ϱch(r) and the magnetization density ϱmg(r), in the rest frame of the proton, are obtained from the experimental data on elastic electron-proton scattering. It is found that these densities are very similar for distances r such that 0.3 fermi ⩽ r ⩽ 1.5 fermi. However, they are clearly different for distances r less than 0.2 fermi. The difference is more easily seen in the Fourier transforms of ϱch(r) and ϱmg(r) obtained from the electric and magnetic form factors. Moreover, one can conclude that ϱch(r) is compatible with a singular behavior for r → 0.