CHARGED LEPTONS WITH NANOSECOND LIFETIMES

Some extensions of the standard model contain additional leptons which are vectorlike under weak isospin. A class of models is considered in which these leptons do not appreciably mix with the known leptons. In such models, the heavy charged lepton and the heavy neutrino are dege nerate in mass, and the degeneracy is broken by radiative corrections. The mass splitting is calculated and found to be very weakly dependen t on the lepton mass, varying from 250 to 330 MeV as the mass varies f rom 100 to 800 GeV. This result is not affected significantly by inclu sion in a supersymmetric model in spite of the additional loops involv ing the superpartners. As a result, this fairly general class of model s has a charged lepton whose lifetime varies in the narrow range from 0.5 to 2.0 nsec, and which decays into neutrals plus a very low energy electron or muon.