Multiple Pion Production by1.89−BeVcπ

A report is given of a study of pion-proton interactions in a liquid-hydrogen bubble chamber. A $1.89-\frac{\mathrm{BeV}}{c}$ negative-pion beam incident upon a 14-in.-diam chamber caused interactions from which those with four charged secondaries were selected and measured. Fits were attempted to the following states: $3\pi +p$, $3\pi +p+{\pi }^0$, and $4\pi +n$. The branching ratios for these three reactions were found to be (64.9±3.3)%, (21.5±1.7)%, and 13.9±1.3)%, respectively. The $3\pi +p$ reaction was found to be dominated by the production of the $\frac{3}{2}-\frac{3}{2}$ pion-nucleon isobar, (43±3)% of these events going via this channel. Evidence for the $\eta$ and $\omega$ mesons was found in the $3\pi +p+{\pi }^0$ final state, (9.0±2.2)% of these events going via the $\eta$ channel, and (14.0±2.8)% via the $\omega$ channel.