One-loop-induced fermion masses and exotic interactions in a standard-model context

The standard SU(2)×U(1) electroweak gauge model is extended to include a fourth generation of quarks and leptons as well as four extra Higgs-boson doublets. With the implementation of a $Z_4$ discrete symmetry, which is softly broken down to $Z_2$, realistic radiative quark and lepton masses for the first two generations can be obtained. Assuming that the third and fourth lepton generations are odd under the unbroken $Z_2$, we discuss a number of interesting phenomenological consequences such as a longer $\tau$ lifetime and some possible anomalous $\tau$ interactions. We also single out some processes involving fourth-generation quarks and leptons which cannot be confused experimentally with those of the standard model.