Photon-Proton and Photon-Photon Scattering from Nucleon-Nucleon Forward Amplitudes

We show that the data on γp and γγ interactions can be derived from the pp and p̄p forward scattering amplitudes using vector meson dominance and the additive quark model. The nucleon–nucleon data are parameterized using a model where high energy cross sections rise with energy as a consequence of the increasing numbers of soft partons populating the colliding particles. We present detailed descriptions of the data on the total and elastic cross sections, the ratio of the real to imaginary part of the forward scattering amplitude, and on the slope of the differential cross sections for pp, p̄p, γp, γγ, γp → γV and γγ → ViVj reactions, where V = ρ, ω, φ. We make a wide range of predictions for future HERA and LHC experiments and for γγ measurements at LEP. Work partially supported by Department of Energy contract DA-AC02-76-Er02289 Task B. Work supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). Work partially supported by Department of Energy Grant No. DE-FG02-95ER40896 and the University of Wisconsin Research Committee with funds granted by the Wisconsin Alumni Research Foundation.