A Remark on the Strangenss and Isotopic Spin for Leptons
Takao Okabayashi, Seitaro Nakamura, Yoshio Nisiyama · Progress of Theoretical Physics · 1961
It is examined whether the strangeness and isotopic spin assignment for leptons proposed by Gamba, Marshak, Okubo and Klein fits the leptonic weak interactions to the same extent as in the case of the weak interactions between baryons and mesons.It is shown that there should exist two kinds of neutral massless lepton (ordinary and strange neutrino) in order to accept the selection rule j.dSj =I.Then the all observed weak interactions satisfy this rule, but the strangeness assignment allows some strangeness conserving leptonic processes such as• K0-7p.++e-andK+-'?p.++e-+n+.Further, there are some undesirable processes in which strangeness changes by one unit, for instance, p.+-72e++e-and p.-+p-7p+e-.At the present status of experiments, it is impossible to get any definite conclusion about the isotopic spin selection rule.It is however shown that, except for p.-7e+Y+ii, p.-+p-7n+Y and probably n--7 p.+Y, the selection rule jAil =1/2 may be regarded to hold in fairly good approximation, if we restrict ourselves to the interactions in which the strangeness change is ±1.The significance of the existence of the aforementioned important exceptional cases is discussed.