π−p Interactions at 2.7 BeVc (Four-Prong Events)

This report is based on the study of 8115 four-prongs produced by the interactions of $2.7\ensuremath{-}\frac{\mathrm{BeV}}{c{\ensuremath{\pi}}^{\ensuremath{-}}}$ mesons with protons in the Lawrence Radiation Laboratory 72-in. hydrogen bubble chamber. The total four-prong cross section is found to be 5.01\ifmmode\pm\else\textpm\fi{}0.12 mb, and the cross sections for each of the final states are: (${\ensuremath{\pi}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$, 1.83\ifmmode\pm\else\textpm\fi{}0.05 mb), (${\ensuremath{\pi}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$, 1.53\ifmmode\pm\else\textpm\fi{}0.04 mb), (${\ensuremath{\pi}}^{\ensuremath{-}}n{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}$, 0.67\ifmmode\pm\else\textpm\fi{}0.02 mb), [${\ensuremath{\pi}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}(m{\ensuremath{\pi}}^{0})$, ($m\ensuremath{\ge}2$), 0.44\ifmmode\pm\else\textpm\fi{}0.02 mb], and [${\ensuremath{\pi}}^{\ensuremath{-}}n{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+} (m{\ensuremath{\pi}}^{0})$, ($m\ensuremath{\ge}1$), 0.54\ifmmode\pm\else\textpm\fi{}0.02 mb]. The final-state ${\ensuremath{\pi}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ is dominated by the production of ${N}^{*++}(1238)[(42\ifmmode\pm\else\textpm\fi{}4)%]$ and ${\ensuremath{\rho}}^{0}[(38\ifmmode\pm\else\textpm\fi{}9)%]$, and the final-state ${\ensuremath{\pi}}^{\ensuremath{-}}n{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}$ by the production of ${N}^{*\ensuremath{-}}(1238)[(72\ifmmode\pm\else\textpm\fi{}12)%]$. The fractions of $\ensuremath{\omega}$ and ${N}^{*++}(1238)$ production in the channel ${\ensuremath{\pi}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$ are estimated to be (32\ifmmode\pm\else\textpm\fi{}4)% and (20\ifmmode\pm\else\textpm\fi{}5)%, respectively. Also presented are the effective-mass plots, production angular distributions, and decay angular correlations.