Pomeranchuk-Exchange Contribution to Forward Photon Processes

Assuming pure Regge-pole behavior and the crossing relations for helicity amplitudes, we show that (1) the Pomeranchuk trajectory does not contribute to Compton scattering from spin-0 or spin-{} particles in the forward direction; (2) Pomeranchuk exchange does contribute to forward vector-meson photoproduction, and at high energies the production of vector mesons with helicity±{}1 dominates over the production of those with zero helicity. Some interesting properties of the crossing relations are derived and used to obtain these results. We briefly discuss the difficulties associated with conclusion (1).