Role of the annihilation channel in investigating low-energy γp scattering

The paper gives the most complete account of the annihilation channel pp-bar → γγ in the dispersion relations for the γp scattering amplitudes. The amplitudes of the processes pp-bar → ππ and ππ → γγ are determined with the help of fixed-t dispersion relations. A new analysis of γp scattering for ν< or approx. =400 MeV is carried out. As a result, the disagreement of the theory with experiment in the Δ (1236)-resonance region is considerably reduced. The influence of the pp-bar → γγ process on the proton polarizability values obtained from the experimental γp scattering data as well as from the sum rules is investigated. The predictions of the sum rules agree with experiment