Muon Decay Width and Lifetime in the Standard Model

Abstract

In this thesis we studied the muon decay μ → eνeνμ according to the standard model (SM). We computed the decay width ����μ and lifetime τμ for leptonic muon , We found their values ����μ = 1 2.19×10−6 Second−1 and τμ = 2.19×10−6 second respectively, these results showed a good agreement with the experimental results. We Used the obtained value of τμ with the given muon mass to determine the Fermi coupling of weak interaction Gf . In addition, We have calculated the value of g2, this is the weak coupling constant in the standard model, we found that: α2 = 1 29 which is larger than the fine structure constant of the electromagnetic interaction, that is: α1 = 1 137 . Consequently, the weak interaction is actually found to be not ”weak”, as the word ”weak” reflect meaning.