Muon Decay in Nuclear Emulsion at 25 000 Gauss

Abstract

Positive pions from the 90-Mev pion beam of the Nevis cyclotron were stopped in nuclear emulsion which was in a magnetic field of 25 000 gauss. The asymmetry parameter for the angular distribution of the positrons which came from the decay muons was measured. The result that $P\ensuremath{\xi}=\ensuremath{-}0.87\ifmmode\pm\else\textpm\fi{}0.04$ implies that either the asymmetry parameter $\ensuremath{\xi}$ is different from the value of -1 predicted by the V-A theory or that there is about 13% depolarization of positive muons in nuclear emulsion at 25 000 gauss.