Star Production by Negativeμ-Mesons in a Silver Chloride Crystal

Abstract

A silver chloride crystal has been used to detect $\ensuremath{\mu}$-mesons which stop in the crystal or in some brass immediately below it. It is found that such mesons and their decay electrons produce pulses well above noise and with rise times of 0.2 to 0.35 \ensuremath{\mu}-sec. On the basis of 79 decay events, the meson mean life is found to be 1.9\ifmmode\pm\else\textpm\fi{}0.3 \ensuremath{\mu}-sec. By comparing the pulse height distribution for stopped mesons with the distribution for the hard cosmic-ray component, it is shown that the crystal response is proportional to energy loss for slow, heavily ionizing particles. During an experimental run 263 mesons stop. Forty are observed to decay, and it is calculated that 78 are negative mesons which stop in the crystal. It is first shown that, in general, nuclear capture of negative $\ensuremath{\mu}$-mesons does not result in the production of stars in which the charged particles carry on the average half the meson rest energy. Further analysis shows that, if stars are produced, the average energy of the charged particles is but a very few Mev, probably less than 3 Mev. Five large pulses associated with stopped particles might be interpreted as star pulses, but some of these may be due to stopped protons.