Antihyperon Production in Antiproton-Proton Reactions at 3.7 BeV/c

Abstract

Results on the production of antihyperons in the reactions of 3.7 BeV/c antiprotons with protons are presented. Examples were observed of the production of the antiparticles of all the baryons with hypercharge 0 and 1, several of which had not been observed prior to this experiment. The mass and lifetime of the $\overline{\Lambda }$ and the lifetimes of the ${\overline{\Sigma }}^{\pm }$ were measured and are consistent with the corresponding quantities of the $\Lambda$ and ${\Sigma }^{\pm }$, as required by $\mathrm{CPT}$ invariance. In the two-body $\Lambda \overline{\Lambda }$, $\Lambda {\overline{\Sigma }}^0$, $\overline{\Lambda }{\Sigma }^0$, and ${\Sigma }^{+}{\overline{\Sigma }}^{-}$ final states the antihyperons displayed a very sharply forward peaked angular distribution. The production of the three-body final states $Y\overline{Y}\pi$ and $\Lambda \overline{N}K$ or $\overline{\Lambda }N\overline{K}$ tend to proceed through the $Y{\overline{Y}}^{*}$ or $\overline{Y}{Y}^{*}$ intermediate states, where the $Y^{*}$ is either the ${Y_1}^{*}\mathrm{}\left(1385\right)\mathrm{}$, the ${Y_0}^{*}\mathrm{}\left(1405\right)\mathrm{}$, or the ${Y_0}^{*}\mathrm{}\left(1520\right)\mathrm{}$. The four-body $\Lambda \overline{\Lambda }{\pi }^{+}{\pi }^{-}$ final state is dominated by the pair production of the ${Y_1}^{*}\mathrm{}\left(1385\right)\mathrm{}$ hyperon isobar.