Four models are considered which contain heavy leptons beyond the three families of the standard model. Two are fourth-generation extensions of the standard model in which the right-handed heavy leptons are either isosinglets or in an isodoublet; the other two are motivated by the aspon model of $\mathrm{CP}$ violation. In all these models, the heavy neutrino can either be heavier than, or comparable in mass to, the charged lepton leading to the possibility that the charged lepton is very long lived. Production cross section and signatures for such leptons are computed for the SSC and CERN LHC.

• Received 31 March 1993

DOI:https://doi.org/10.1103/PhysRevD.48.3128