HYPERON PRODUCTION IN INTERACTIONS OF 2.7 GeV/c ANTIPROTONS ON PROTONS.

We have measured the cross sections for hyperon production in 2.7-GeV/c $\overline{p}p$ interactions. The values obtained are: $\ensuremath{\sigma}(\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda})=113\ifmmode\pm\else\textpm\fi{}15 \ensuremath{\mu}\mathrm{b}, \ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{0}\ensuremath{\Lambda})+\ensuremath{\sigma}(\overline{\ensuremath{\Lambda}}{\ensuremath{\Sigma}}^{0})=66\ifmmode\pm\else\textpm\fi{}13 \ensuremath{\mu}\mathrm{b},$ $\ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{0}{\ensuremath{\Sigma}}^{0})l15 \ensuremath{\mu}\mathrm{b}, \ensuremath{\sigma}({\overline{\ensuremath{\Xi}}}^{0}{\ensuremath{\Xi}}^{0})=\ensuremath{\le}2.8 \ensuremath{\mu}\mathrm{b}(90% \mathrm{confidence})$ $\ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}{\ensuremath{\Sigma}}^{+})=30.7\ifmmode\pm\else\textpm\fi{}9.4 \ensuremath{\mu}\mathrm{b}, \ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{+}{\ensuremath{\Sigma}}^{\ensuremath{-}})=1.0\ifmmode\pm\else\textpm\fi{}5.4 \ensuremath{\mu}\mathrm{b} (\mathrm{large}\mathrm{error}\mathrm{resulting}\mathrm{from}\mathrm{subtraction}),$ $\ensuremath{\sigma}({\overline{\ensuremath{\Xi}}}^{+}{\ensuremath{\Xi}}^{\ensuremath{-}})=\ensuremath{\le}1.8 \ensuremath{\mu}\mathrm{b} (90% \mathrm{confidence}), \ensuremath{\sigma}(\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda}{\ensuremath{\pi}}^{0})=65\ifmmode\pm\else\textpm\fi{}25 \ensuremath{\mu}\mathrm{b},$ $\ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}+\mathrm{c}.\mathrm{c}.)=25.9\ifmmode\pm\else\textpm\fi{}10.1 \ensuremath{\mu}\mathrm{b}, \ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}{\ensuremath{\Sigma}}^{0}{\ensuremath{\pi}}^{+}+\mathrm{c}.\mathrm{c}.)=2.9\ifmmode\pm\else\textpm\fi{}2.9 \ensuremath{\mu}\mathrm{b} (\mathrm{one}\mathrm{event}),$ $\ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{+}\ensuremath{\Lambda}{\ensuremath{\pi}}^{\ensuremath{-}}+\mathrm{c}.\mathrm{c}.)=6.6\ifmmode\pm\else\textpm\fi{}3.9 \ensuremath{\mu}\mathrm{b}, \ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{+}{\ensuremath{\Sigma}}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}+\mathrm{c}.\mathrm{c}.)=3.7\ifmmode\pm\else\textpm\fi{}2.6 \ensuremath{\mu}\mathrm{b},$ $\ensuremath{\sigma}({\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}{\ensuremath{\Sigma}}^{+}{\ensuremath{\pi}}^{0})=\ensuremath{\le}3.6$ \ensuremath{\mu}b (90% confidence), $\ensuremath{\sigma}(\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})=3\ifmmode\pm\else\textpm\fi{}2$ \ensuremath{\mu}b, and $\ensuremath{\sigma}(\ensuremath{\Lambda}{K}^{+}\overline{p})=2.3\ifmmode\pm\else\textpm\fi{}2.3$ \ensuremath{\mu}b (one event). The ratios of the cross sections for the two-body final states have been compared with predictions of $S{U}_{3}$ and are in good agreement with the process being dominated by the exchange of an antisymmetric octet in the $t$ channel. The angular distributions of $\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda}$, ${\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}{\ensuremath{\Sigma}}^{+}$, and $\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda}{\ensuremath{\pi}}^{0}$ final states clearly show the peripheral nature of these interactions. The differential cross section data for the interaction $\overline{p}p\ensuremath{\rightarrow}\overline{\ensuremath{\Lambda}}\ensuremath{\Lambda}$ have been compared with parametric equations and three absorption models. Good fits to the data have been achieved with each of these equations or models.