Radiative corrections to the beam-normal spin asymmetry in elastic electron scattering from Pb208

Estimates for the quantum electrodynamical (QED) and dispersion effects on the spin asymmetry of perpendicularly polarized electrons scattered from a ^208Pb nucleus are given. The QED effects are calculated nonperturbatively in terms of their respective potentials. For dispersion, the transient nuclear excitations of ^208Pb with low multipolarity and energy below 30 MeV are accounted for. Collision energies up to 1 GeV are considered. The results can help to explain the measured spin asymmetry near 1 GeV at forward angles.