Associated Production of Strange Particles by 1.1-Bevπ−Mesons

Abstract

The associated production of strange particles by 1.1-Bev kinetic energy ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons by the reactions $(1) {\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{\ensuremath{-}}+{K}^{+},$ $(2) {\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}+{\ensuremath{\theta}}^{0},$ $(3) {\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{0}+{\ensuremath{\theta}}^{0},$ has been studied in a 12-in. propane bubble chamber. The total cross sections in hydrogen for the above reactions are 0.17\ifmmode\pm\else\textpm\fi{}0.04 mb, 0.22\ifmmode\pm\else\textpm\fi{}0.06 mb, and 0.21\ifmmode\pm\else\textpm\fi{}0.06 mb, respectively. In the ${\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{-}p$ center-of-mass, the ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ is produced in the forward direction while the ${\ensuremath{\Lambda}}^{0}$ and ${\ensuremath{\Sigma}}^{0}$ are produced in the backward direction. Lifetimes for the ${\ensuremath{\Sigma}}^{\ensuremath{-}}$, ${\ensuremath{\Lambda}}^{0}$, and ${\ensuremath{\theta}}^{0}$ are found to be (1.6${7}_{\ensuremath{-}0.28}^{+0.48}$)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ sec, (${2.24}_{\ensuremath{-}0.48}^{+0.79}$)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ sec, and (${0.74}_{\ensuremath{-}0.15}^{+0.21}$)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ sec, respectively. From various angular distributions of decay products, we find that the data are consistent with spin 1/2 for the ${\ensuremath{\Lambda}}^{0}$ and ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ and spin 0 for the ${\ensuremath{\theta}}^{0}$. The data are also consistent with parity conservation in strange-particle decay.