Meson Production in Nucleon-Nucleon Collisions at High Energies

Abstract

Calculations based on a statistical model have yielded results concerning the relative probabilities for the different multiplicities and charge distribution of mesons produced in nucleon-nucleon collisions. In deviating from a pure statistical model the important effects of final state interactions and various selection rules have been included, using results of meson-nucleon scattering experiments. Notably in the results the suppression of some one-meson final states by consideration of the Pauli principle and conservation of angular momentum and parity, along with the enhancement of two-meson states due to resonance effects, have brought about results which are in closer agreement with experiment than predictions of a pure statistical nature. Account was taken of the final state interactions by considering separately the nucleon-nucleon and meson-nucleon interactions, a separation made plausible by consideration of the small amount of kinetic energy taken away by the more massive particles. Meson-meson interactions were neglected. The nucleon-nucleon interaction was taken care of by introducing in the statistical weight a factor which is the square of the wave function for the scattering of two nucleons evaluated at the origin of their interaction. The meson-nucleon final state scattering was treated by the method discussed by Chew, modified for the case of a meson scattering off two stationary and superposed nucleons. Multiplicities up to two mesons were considered. On comparing with experimental results, at 1.7-Bev bombarding energy of neutrons on protons the ratio of the probability of occurrence of the final states $(np+\ensuremath{-}):(pp\ensuremath{-}0):(pp\ensuremath{-})$ is calculated to be 3.0:1.0:0.9, while experiment gives 3.3:1:0.8. The ratio of the total probability for double meson production to that for single meson production at this energy is 1.2, while a modified result of observations gives 1.4. Results on proton-proton collisions do not yield good agreement with present observations.