Two-Meson Annihilations of 1.61-BeV/<i>c</i>Antiprotons in Hydrogen

Abstract

Proton-antiproton annihilations at 1.61 BeV/c with only two mesons in the final state have been examined in the 72-in. bubble chamber. The partial cross sections measured are $\overline{p}+p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}+{\ensuremath{\pi}}^{+}, 119\ifmmode\pm\else\textpm\fi{}30\ensuremath{\mu}\mathrm{b};$ $\overline{p}+p\ensuremath{\rightarrow}{K}^{\ensuremath{-}}+{K}^{+}, 55\ifmmode\pm\else\textpm\fi{}18\ensuremath{\mu}\mathrm{b}.$ The ${K}^{\ensuremath{-}}$ distribution in $\overline{p}+p\ensuremath{\rightarrow}{K}^{\ensuremath{-}}+{K}^{+}$ is peaked strongly forward, with 7 of the 11 ${K}^{\ensuremath{-}}$ mesons produced in the forwardmost tenth of the total solid angle. The ${\ensuremath{\pi}}^{\ensuremath{-}}$ events show no such effect, with only 2 of the 22 ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons being produced in the same forward interval. Careful study of possible contamination of these events indicates that almost all of them are genuine two-meson annihilations.