AV-Decay Event with a Heavy Negative Secondary, and Identification of the SecondaryV-Decay Event in a Cascade

Abstract

Two cosmic-ray decay events have been photographed in a cloud chamber under conditions that yield mass values from combined magnetic-field momentum measurements and ionization measurements from droplet counting. A method has been developed for assigning meaningful probable errors to the ionization measurements. The first event is interpreted as the decay of a neutral $V$ particle into a positive $\pi$ meson and a negative particle of mass $1850\pm 250m_e$. On the assumption of a two-body decay, the $Q$ value for the decay is 11.7±4 Mev. The second event is a cascade decay that can be summarized by the following reaction: $\{Y^{-}\to 67\pm 12 \mathrm{Mev}+{\pi }^{-}+{\Lambda }^0\}\left\{\searrow \right\}\{40\pm 13 \mathrm{Mev}+{\pi }^{-}+p.\mathrm{}\}$ The proton of the ${\Lambda }^0$ decay is identified by a measured mass of $2050\pm 350m_e$. On the assumption of a twobody decay, the mass of the primary $V$ particle is $2600\pm 34m_e$.