Influence of absorption due to competing processes on peripheral reactions

Summary  The peripheral or one-meson-exchange model is modified to include absorptive effects due to competition from other inelastic channels. These effects are most important for small impact parameters (low partial waves) and produce an appreciable reduction in cross-section, and a pronounced collimation of the angular distribution. The absorption thus provides a natural explanation of the highly peaked angular distributions previously ascribed toad hoc form factors. The necessary information concerning the absorption is inferred from the elastic scattering in the initial and final state in a manner first proposed by Sopkovich. Because of the importance of the decay correlations of resonances produced in these reactions, the spins of the particles are treated in a consistent way. It is found that a proper treatment of the spins is also essential in evaluating the angular distribution of production. The reaction π-p → ρ-p at 4 GeV/c is discussed in detail; the theoretical cross-section is in good agreement with experiment, both as to angular dependence and absolute value. The p-meson’s spin density matrix is found to be altered somewhat from the unmodified one-pion-exchange results, especially at larger production angles. The calculated density matrix is in agreement with the available data on the decay correlations.