Hyperon Production in Interactions of 2.7-GeV/cAntiprotons on Protons

Abstract

We have measured the cross sections for hyperon production in 2.7-GeV/c $\overline{p}p$ interactions. The values obtained are: $\sigma \left(\overline{\Lambda }\Lambda \right)=113\mathrm{}\pm 15 \mu \mathrm{b}, \sigma \left({\overline{\Sigma }}^0\Lambda \right)+\sigma \left(\overline{\Lambda }{\Sigma }^0\right)=66\mathrm{}\pm 13 \mu \mathrm{b},$ $\sigma \left({\overline{\Sigma }}^0{\Sigma }^0\right)<\mathrm{}15\mathrm{} \mu \mathrm{b}, \sigma \left({\overline{\Xi }}^0{\Xi }^0\right)=\le 2.8 \mu \mathrm{b}(90\% \mathrm{confidence})$ $\sigma \left({\overline{\Sigma }}^{-}{\Sigma }^{+}\right)=30.7\mathrm{}\pm 9.4 \mu \mathrm{b}, \sigma \left({\overline{\Sigma }}^{+}{\Sigma }^{-}\right)=1.0\mathrm{}\pm 5.4 \mu \mathrm{b} \left(\mathrm{large}\mathrm{error}\mathrm{resulting}\mathrm{from}\mathrm{subtraction}\right),$ $\sigma \left({\overline{\Xi }}^{+}{\Xi }^{-}\right)=\le 1.8 \mu \mathrm{b} (90\% \mathrm{confidence}), \sigma \left(\overline{\Lambda }\Lambda {\pi }^0\right)=65\mathrm{}\pm 25 \mu \mathrm{b},$ $\sigma ({\overline{\Sigma }}^{-}\Lambda {\pi }^{+}+\mathrm{c}.\mathrm{c}.\mathrm{})=25.9\mathrm{}\pm 10.1 \mu \mathrm{b}, \sigma ({\overline{\Sigma }}^{-}{\Sigma }^0{\pi }^{+}+\mathrm{c}.\mathrm{c}.\mathrm{})=2.9\mathrm{}\pm 2.9 \mu \mathrm{b} \left(\mathrm{one}\mathrm{event}\right),$ $\sigma ({\overline{\Sigma }}^{+}\Lambda {\pi }^{-}+\mathrm{c}.\mathrm{c}.\mathrm{})=6.6\mathrm{}\pm 3.9 \mu \mathrm{b}, \sigma ({\overline{\Sigma }}^{+}{\Sigma }^0{\pi }^{-}+\mathrm{c}.\mathrm{c}.\mathrm{})=3.7\mathrm{}\pm 2.6 \mu \mathrm{b},$ $\sigma \left({\overline{\Sigma }}^{-}{\Sigma }^{+}{\pi }^0\right)=\le 3.6$ μb (90% confidence), $\sigma \left(\overline{\Lambda }\Lambda {\pi }^{+}{\pi }^{-}\right)=3\mathrm{}\pm 2$ μb, and $\sigma \left(\Lambda K^{+}\overline{p}\right)=2.3\mathrm{}\pm 2.3$ μb (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 $\overline{\Lambda }\Lambda$, ${\overline{\Sigma }}^{-}{\Sigma }^{+}$, and $\overline{\Lambda }\Lambda {\pi }^0$ final states clearly show the peripheral nature of these interactions. The differential cross section data for the interaction $\overline{p}p\to \overline{\Lambda }\Lambda$ 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.