Radiative Corrections to Elastic Electron-Proton Scattering for Polarized Electrons

We analyze the radiative correction to high energy elastic electron-proton scattering of polarized electrons. We show that if the approximations inherent in the calculations developed by Tsai and given in the work of Mo and Tsai, which have been used in the analysis of almost all experimental data pertain- ing to medium and high energy elastic electron scattering for the past three decades, are maintained, then the same radiative correction applies both in the case of initially polarized and unpolarized electrons. and longitudinal polarizations of the recoil protons were measured in order to obtain the ratio of the proton's elastic electromagnetic form factors, GEp /GMp . Given that radiative corrections to elastic electron-proton scattering are generally of the order of 20% - 30% for four-momentum transfer squared in the range considered in these experiments (0.5 to 3.5 (GeV/c) 2 ), the question arises as to whether the same radiative correction used in the case of unpolarized beams and targets can be applied in the case of polarized electron beams when the polarization of the recoil proton is measured. We show here that if the approxi- mations inherent in the calculations developed in (1) and given in (2) are maintained, then the same radiative correction applies both in the case of initially polarized and unpolarized electrons. In Sec. II we present the cross section for the scattering of polarized electrons from unpolarized protons in the absence of radiative corrections. In Sec. III we give each of the matrix elements associated with the radiative correction and discuss the significant approximations that are made in (1) to evaluate their contribution to the cross section. We then show that with these approximations the radiative corrections do not depend on the polarization of either the electron or the proton in the initial or final state.