Poles and Resonances inηProduction

Abstract

Poles and resonances are used to find y^ fits to the data up to several hundred MeV above threshold for the processes iT-^p -^ n-^-fi and y-\-p -^ p+v-Below center-of-mass energy 1^=1700 MeV, a consistent picture of these reactions is achieved with the following ingredients: a nucleon pole and Pu (1400), 5ii (1570), and J9i3 (1512) resonances for production by pions; a nucleon pole, a vector meson pole, and 5ii(1570) and DIB(1512) resonances for photoproduction. Some Fi6(1688) also improves the fits. The value of therj-nuchon coupling constant, g"V47r is < 0.002 in both processes. Implications of these results for quark models and SUiS) symmetry are discussed.