Single Neutral Pion Production by Pions at 1100 Mev

Well-identified events of the type ${\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}p+{\ensuremath{\pi}}^{\ensuremath{-}}+{\ensuremath{\pi}}^{0}$ were obtained by requiring, in addition to satisfaction of kinematic criteria, that the production of the neutral pion be verified by observation of either a $\ensuremath{\gamma}$-ray conversion electron pair or a Dalitz-decay pair associated with the interaction. In a scan of 100 000 Bevatron photographs 70 acceptable events were found. The kinematic behavior of the selected events did not agree with the predictions of the isobar model, but was consistent with the assumption that the events were initiated by a strong pion-pion interaction, with subsequent rescattering of pions by the nucleon. There is some indication that two $T=1$ dipion states with total energies of 565 and 750 Mev are involved in the interactions.