Reanalysis of ep Elastic Scattering Data in Terms of Proton Electromagnetic Formfactors

Abstract

We have made the comparison of three parametrizations of the proton electromagnetic form factors in the space-like region using the largest data set on $e^{\pm} p$ elastic scattering ever used. All models have a correct analytical structure with a minimal set of well known singularities. For the first time an effective two-pion intermediate coulombic bound state (pionium) was included into GVMD for nucleon formfactors. For the proton charge radius an estimate derived from our best fits is as follows: r_E^p [\rm fm] = 0.897 \pm 0.002(exp) \pm 0.001(norm) \pm 0.003(models). The traditional ``model independent'' fit by quadratic polynomial gives, in our estimation technology, a much cruder estimate r^p_{E,polinomial} [\rm fm] = 0.887 \pm 0.006(exp) \pm 0.096(norm). Both estimates are closer to the value estimated from the recent hydrogen Lamb shift measurements.