Tviolation in SU(2) × U(1) gauge theories of leptons

Theories are studied in which violation of time-reversal invariance occurs in the leptons due to complex gauge couplings. We study under what conditions $T$ violation may be present in a theory, and give three SU(2) × U(1) models (including an extension of the Cheng-Li model) to serve as examples of general classes of models. The electric dipole moment of the electron and $T$-violating correlations in leptonic decays are discussed. In general $T$-violating effects are difficult to observe even if the $T$-violating parameters are large. However, if heavy neutral leptons are found in neutrino scattering, a relatively simple $T$-violation test is discussed.