Gamma Rays from Strange Particles

Abstract

Strange-particle production by protons in the Cosmotron range of energies was studied by observing gamma rays resulting from the decay of these particles at distances a few centimeters from the bombarded target. A laboratory energy threshold of 1.1±0.1 Bev was measured for protons on a copper target, consistent with the hypothesis of associated production. A free-particle threshold is estimated. The production below threshold, at 1.0 Bev, is less than ${10}^{-2\mathrm{}}$ of the 2.9-Bev production. The mean survival distance for particles produced at 1.7 Bev is 3.8 cm. Upon analysis this yields a lifetime which matches the one known for the ${\theta }^0$ and suggests ${\theta }^0\to 2{\pi }^0$. Unless the ${\Lambda }^0$ is produced with a strongly (${cos}^2\theta$) peaked forward and backward angular distribution, it cannot be the dominant source of the gamma rays. Under the assumption that these particles are hyperons or heavy mesons, the total cross section, of that component which decays via ${\pi }^0$ mesons, is 0.1 mb per carbon nucleus.