Production Of Eta Mesons In Nucleon-Nucleon Collisions

A microscopic calculation of near-threshold eta-meson production in the reaction NN-->NNeta is presented. It is assumed that the eta meson is produced via direct emission and via elementary rescattering processes MN-->etaN of various mesons M=pi, rho, etc. As a novel feature the amplitudes for the latter production mechanism are taken from a multichannel meson-exchange model of the piN system developed by the Julich group which contains explicitly the channels piN, rhoN, etaN, sigmaN, and piDelta. Furthermore, effects of the NN interaction in the final as well as in the initial state are taken into account microscopically. Our results are compared with recent data from the COSY and CELSIUS accelerator facilities. Reasonable agreement with available near-threshold cross section data for the reactions pp-->ppeta, pn-->pneta, and pn-->deta is found.