$p-p$ Interactions at 2 Bev. II. Multiple-Pion Production

Analyses have been made for 871 four-prong events and 463 two-prong events corresponding to multiple pion production, resulting from $p-p$ interactions at 2 Bev in the BNL 20-in. hydrogen bubble chamber. Cross sections have been obtained for all the observable double and triple pion production processes; the branching ratios predicted by the extended isobar model are shown to be in fair agreement with the data, but there are significant differences. The c.m. momentum distributions are also in fair agreement with the predictions of the model, although there are ambiguities in the interpretation. The pion-nucleon $Q$ values give clear evidence for the importance of the ($\frac{3}{2}, \frac{3}{2}$) resonant state in multiple pion production, but consideration of this state alone does not provide an explanation of the features of double pion production. Some contribution from another state, possibly the $I=\frac{1}{2}$ nucleon isobar, is necessary. In double production, the c.m. angular distributions of the nucleons show backward-forward peaking suggestive of a one-pion exchange process. The angular distributions of the nucleons from triple production are almost isotropic.