Polarization of the recoil protons in the elastic electron-proton scattering process

Abstract

The imaginary part of the two-photon-exchange amplitude is estimated in an isobar model and used to calculate the polarizationP of the recoil protons in elastic (e, p)-scattering processes. Using the unitarity relation for the imaginary part, the sum over the intermediate states is approximated by a sum over nucleon isobars. The spin summations are performed for arbitrary half-integer spinj isobars to obtain an expression forP where the isobaric transition form factors are the only unknown quantities. Numerical calculations have been done forN andN*(1236) contributions only. Forɛilab ≈ 550 MeV and a momentum transfer of about 0.25 (GeV/c)2 the maximum value forP was obtained to be about −0.5%.