UnstableH41Fragment from the Capture of aΣ−Hyperon

Abstract

A 10×15×5 cm stack of Ilford G-5 emulsion was exposed to the 3.0-Bev ${\pi }^{-}$-meson beam of the Berkeley Bevatron. A number of events involving $K$-mesons, hyperons, and hyperfragments have been observed. One interesting case is discussed here. A nine prong star is produced by a ${\pi }^{-}$ meson, from which a ${\Sigma }^{-}$ hyperon emerges. This in turn produces a star with three visible prongs, one of which is a ${}_1{}^{}{}_{}{}^{}\mathrm{H}_{}^4{}_{}{}^{}$-hyperfragment decaying into two visible colinear tracks, one of which has been identified as a ${\pi }^{-}$ meson. This ${\pi }^{-}$ meson was followed to the end of its range, and its energy was determined to be 51±1 Mev, making it possible to calculate a reliable value for the binding energy of the ${\Lambda }^0$ in the fragment. The result yielded 3.3±1 Mev. Analysis of the particles emerging from the ${\Sigma }^{-}$ star showed that momentum balance could be achieved by assuming emission of a high-energy neutron, whose calculated energy of 41 Mev agrees well with the energy of 42 Mev for a neutron produced in the postulated elementary interaction ${\Sigma }^{-}+p\to {\Lambda }^0+n+Q$.