Abstract: | Due to the possible production of neutral and charge heavy leptons by vμ, models consisting of four elements per "line", e.g. ve, e-, E0, E- vμ, μ-, M0, M- vτ, τ-, T0, T- ……are analysed. Non-diagonal neutral currents cannot be avoided. Nevertheless, a model is proposed within SU(2)×U(1) in which the process μ→eγ can still be suppressed by the Bjorken-Lane-Weinberg mechanism; various production cross-sections for heavy leptons are reasonable when compared with experiments. Models corresponding to SU(3)×U(1) and still higher symmetries are discussed. |