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 ${\pi }^{+}$ mesons of momentum 280 Mev/c leaving the target at 0° in the laboratory system. Correcting for decay in flight, the $\frac{{\pi }^{+}}{K^{+}}$ ratios are (630±110), (290±48), and (304±50) for the respective hydrogen, lithium, and copper targets. The laboratory system differential cross sections for $K^{+}$ production are (4.8±1.0)×${10}^{-32\mathrm{}}$, (3.5±0.7)×${10}^{-31\mathrm{}}$, and (3.0±0.6)×${10}^{-30\mathrm{}}$ ${\mathrm{cm}}^2$/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 ${cos}^2\theta$ distribution the $p-p$ cross section also happens to be 0.21 mb. The $\frac{\pi }{K}$ ratios indicate that $K^{+}$ production by $p-p$ 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 ${\pi }^{+}$ production. Our integrated cross sections suggest that strange particle production by 3-Bev protons occurs ∼1% of the time.