High-Energy Polarized-Photon Reactions

A general formalism is presented for the analysis of production and decay distributions of meson-baryon final states resulting from interactions of polarized photons and nucleons. Particular emphasis is given to high-energy reactions and Regge-pole exchange models. Circular polarization is shown to provide a test for the presence of two or more exchanges. Linear polarization parallel or perpendicular to the production plane allows the contributions of opposite $J$-parity exchanges to be separated. This formalism enables one to make use of data at all angles, rather than limit consideration to discrete points. Applications include the separation of diffractive and pion-exchange contributions to vector-meson production, and tests for non-pole-type exchanges in baryon-resonance production. Examination of pion photoproduction reveals that no simple test exists for the discrimination between pion conspiracy and evasion models.