On the connection between production mechanism and decay of resonances at high energies

Abstract

The production of unstable particles in peripheral collisions at high energies is considered, with emphasis on the connection between the production mechanism and the angular correlations in the decay of the unstable particles. By means of the crossing relations for helicity amplitudes a direct relation (10) is established between the t-channel helicity amplitudes and the spin-space density matrix (relative to a suitable system of co-ordinate axes) of one of the reaction products. The extent to which the decay angular distributions determine the density matrix is fully discussed. As an example, various quasi-two-body chan of KN collisions are considered, especially KN → K*N It is shown that, while the decay correlations of K* at 3 GeV/c are consistent with dominantly vector-meson exchange, they are also consistent with the exchange of systems with any J ≥1 provided the parity is (-1)J. Advantage is taken of this observation to generalize the one-mesonexchange model by means of Eegge-pole exchange in a way which gives a natural explanation of the very peripheral nature of the production process, while maintaining agreement with the decay data. © 1964 Società Italiana di Fisica.