The weak interactions of the muon - C.E.R.N. work on weak interactions

The relation between the muon and the electron is one of the outstanding puzzles in elementary particle physics today. As far as our present knowledge goes, the interactions of the muon are all of the same form and strength as those of the electron. The differences observed between their interaction rates are accounted for entirely as consequences of their difference in mass value, a difference whose origin is not yet known. Otherwise, the only difference established between the muon and the electron is that their weak interactions involve coupling with two distinct neutrinos, V μ and V e respectively. My paper will be concerned with the accuracy and detail with which we know that the weak interactions of the muon and electron are identical in form. All of the evidence available on these interactions is consistent with the hypothesis that these leptons participate in weak interactions only through the charged current vectors, J l and its Hermitian conjugate J ϯ l , given by J lα = ψ̄ l γ α (1 + γ 5 ) Ψ v , and, for simplicity, we shall confine our attention to this hypothesis here.