Muon Decay

Abstract

The decay of the muon has been studied at PSI with several precision measurements: The longitudinal polarization P_{\mathrm{L}}(E)PL(E) with the muon decay parameters \xi'ξ′, \xi''ξ″, the Time-Reversal Invariance (TRI) conserving transverse polarization P_{\mathrm{T_{1}}}(E)PT1(E) with the muon decay parameters \etaη, \eta''η″, the TRI violating transverse polarization P_{\mathrm{T_{2}}}(E)PT2(E), with \alpha'/Aα′/A, \beta'/Aβ′/A and the muon decay asymmetry with P_{\mu}\xiPμξ. The detailed theoretical analysis of all measurements of normal and inverse muon decay has led for the first time to a lower limit |g^{V}_{LL}| > 0.960|gLLV|>0.960 (“V-AV−A”) and upper limits for nine other possible complex couplings, especially the scalar coupling |g^{S}_{LL}| < 0.550|gLLS|<0.550 which had not been excluded before.