Neutrino oscillation and multiplicative lepton number conservation

The thesis concerns neutrino oscillation and multiplicative lepton number conservation, and is divided into two parts. In the first part, a detailed analysis is given of the effects of massive neutrinos and their subsequent mixing according to the Pilenky-Pontecorvo Scheme, on the branching ratio R = π → eupsilon/π → μupsilon, and on muon decay. It is found that, even for neutrinos having a mass of 20 MeV, the positron spectrum resulting from the decay of polarized muons will be unaffected unless one has no left-handed mixing and maximum possible right-handed mixing. The second part considers e-μ-I universality by using the permutation symmetry group S3 to unify leptons within the Weinberg-Salam SU(2)xU(1) gauge model. The result is a theory in which leptons carry a new multiplicatively conserved quantum number PI=1, esup(2πi/3), esup(4πi/3). (U.K.)