Three-Particle Final States and Unitary Symmetry

A large number of new predictions of $\mathrm{SU}\left(3\right)\mathrm{}$ are obtained for processes with three outgoing particles. All reactions involved in these relations are scattering of charged particles on protons with no more than one neutral particle in the final state. They can all be measured by the present experimental techniques. A detailed comparison between the available data and the predictions is presented, whenever possible. In a few cases, disagreement is found; but when we allow symmetry-breaking contributions within the matrix elements which describe the processes, the data are always consistent with the predictions. The general problem of comparing the predictions of a broken symmetry with scattering data is discussed, and various possibilities for performing such comparisons are suggested.