Implications of the discrepancy between proton form factor measurements

Recent polarization transfer measurements of the proton electromagnetic form factors yield very different results from previous Rosenbluth extractions. This inconsistency implies uncertainties in our knowledge of the form factors and raises questions about how to best combine data from these two techniques. If the discrepancy is due to missing corrections to the cross section data, as has been suggested, then the true form factors, related to the proton structure, differ from the form factors that parametrize the deviation from point scattering, and different applications will require the use of different form factors. We present two extractions of the form factors: a global fit to the world's cross section data, and a combined extraction from polarization transfer and cross section data. The former provides a parametrization of the elastic electron-proton cross section. The latter provides a consistent extraction of the underlying form factors, under the assumption that missing terms in the radiative correction explain the difference between the cross section and polarization transfer results.