Meson exchange models for Meson production

Abstract

The production of mesons in nucleon-nucleon collisions is reviewed from the viewpoint of the meson-exchange picture. In the first part various possible production mechanisms and their relative importance are discussed. In addition, general features of meson production are described. In the second part special emphasis is put on pion production. Implications of chiral perturbation theory are discussed. Results based on a specific meson-exchange model for pion production in nucleon-nucleon collisions are presented. The model is utilized to calculate several spin-dependent observables of the reactions $pp \to pp\pi^0$ and $pp \to pn\pi^+$ such as spin-correlation parameters. This allows us to study the role of the Delta resonance at close to threshold energies. The talk closes with a brief discussion of the production of $\phi$ mesons as an example for the production of heavier mesons. A strategy is outlined that allows to extract information on the structure of the nucleon from the reaction $NN \to NN \phi$.Comment: Invited talk at the 4th International Conference on Physics at Storage Rings (STORI99), Bloomington, IN USA, Sept. 12-16, 1999; 15 pages, 6 figure