Coupled-channel interaction for intermediate-energy nucleon-nucleon reactions

Abstract

General effects of coupling a system to higher-mass channels are reviewed. The dominant effect is the addition of an attraction which increases with energy up to and, when the coupled channel is not in an S state, beyond inelastic threshold. This can produce resonances whose widths and inelasticities are largely determined by the resonance position. A model is presented for nucleon-nucleon channels coupled to N..delta.., NN*, or ..delta delta.. channels. It uses the Feshbach-Lomon nucleon-nucleon interaction and one-pion-exchange potentials plus phenomenological cores for the transition interactions. The width of the isobars is included. Good fits are obtained to NN channels for E/sub L/< or approx. =1 GeV, including the ''resonant'' /sup 1/D/sub 2/ and /sup 3/F/sub 3/ partial waves. A structure may be present in the /sup 3/P/sub 0/ partial wave. In those partial waves where one-pion exchange predicts the largest transition potentials, the fit is improved by the long-range potential tails.