Pseudoscalar meson photoproduction at high energies: from the Regge regime to the hard scattering regime

A model for high energy pion photoproduction is presented which interpolates between the low and high momentum transfer regions. At low momentum transfer (which is described in terms of Regge trajectory exchanges), the model is able to give an economical description of the numerous high energy unpolarized and polarized γN → πN data. At higher momentum transfer, a description based on saturating Regge trajectories and which satisfies quark counting rules at asymptotically large transfers, is found able to describe the few existing γp → nπ+ data. The model can be used as a guidance to interpret forthcoming data at large momentum transfers.