Production Cross Sections ofK+Mesons by 3-Bev Protons on H, Li, and Cu

Abstract

Liquid hydrogen, lithium, and copper targets were exposed to the Cosmotron 3-Bev external proton beam. Nuclear emulsion stacks were used to detect momentum-analyzed ${K}^{+}$ and ${\ensuremath{\pi}}^{+}$ mesons of momentum 280 Mev/c leaving the target at 0\ifmmode^\circ\else\textdegree\fi{} in the laboratory system. Correcting for decay in flight, the $\frac{{\ensuremath{\pi}}^{+}}{{K}^{+}}$ ratios are (630\ifmmode\pm\else\textpm\fi{}110), (290\ifmmode\pm\else\textpm\fi{}48), and (304\ifmmode\pm\else\textpm\fi{}50) for the respective hydrogen, lithium, and copper targets. The laboratory system differential cross sections for ${K}^{+}$ production are (4.8\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}32}$, (3.5\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}31}$, and (3.0\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}30}$ ${\mathrm{cm}}^{2}$/sterad Mev per hydrogen, lithium, and copper nucleus respectively. Assuming a ${K}^{+}$ energy dependence proportional to the final state density (energy independent matrix element) the integrated ${K}^{+}$ production cross sections are 0.21, 1.7, and 14.7 mb for hydrogen, lithium, and copper. For a matrix element proportional to the ${K}^{+}$ momentum in the center of mass and assuming a ${cos}^{2}\ensuremath{\theta}$ distribution the $p\ensuremath{-}p$ cross section also happens to be 0.21 mb. The $\frac{\ensuremath{\pi}}{K}$ ratios indicate that ${K}^{+}$ production by $p\ensuremath{-}p$ is not suppressed significantly relative to that by $p$-nucleus and that the Li to Cu $Z$-dependence of ${K}^{+}$ production appears the same as for ${\ensuremath{\pi}}^{+}$ production. Our integrated cross sections suggest that strange particle production by 3-Bev protons occurs \ensuremath{\sim}1% of the time.