Capture and Decay ofμ−Mesons in Fe

Abstract

The mean life of ${\mu }^{-}$ mesons in Fe has been measured using an improved cosmic-ray apparatus. A positive identification of the stopped muon was made using Čerenkov velocity selectors in the incident telescope. The 2.2-μsec background from positive muons was reduced a factor of 3 with a 3-layer sandwich of Fe and thin plastic scintillators, so arranged that electrons emitted in the target were mostly detected as such by the scintillators. The mean life is 196±8 mμsec. By comparing this result with the electron-counting results of Lederman and Weinrich, the ratio of the decay rate of ${\mu }^{-}$ bound in Fe to the free ${\mu }^{+}$-decay rate is found to be 1.15±0.06.