π−pInteractions at 2.7BeVc(Four-Prong Events)

Abstract

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