Heavy Mesons Produced by 2.2- and 3.0-Bev Protons

Abstract

Emulsions were traversed by radiations from a target bombarded by either 2.2-Bev or 3.0-Bev protons. Analyses of tracks of twelve heavy mesons that came to rest in the emulsions are presented. The stopped heavy mesons produced secondaries showing that 2 were tau mesons, 1 was a negative $K$ meson, and 9 were positive $K$ mesons. Grain count, scattering and range measurements served to determine $K$-meson masses; the average of 6 positive $K$ mesons that could be measured well was $(965\mathrm{}\pm 15)m_e$. Evidence is given, from comparison with existing $p\beta$-blob density curves, that one $K^{+}$ secondary is a muon or electron, while another $K^{+}$ secondary is a pion. If, in the latter case, it is assumed that the $K^{+}$ decays into a charged and a neutral pion, the mass of the $K^{+}$ is found to be $(945\mathrm{}\pm 20)m_e$ and the $Q$ of the decay (207±9) Mev, the same, within experimental error, as for ${\theta }^0$.