Single Heavy Lepton Production in High Energy Electron-Positron   Collisions
  The production and decay of exotic leptons are discussed in the context of the vector singlet, vector doublet and fer\-mion mirror-fer\-mion models, at c.m. energies $\sqrt{s}=190GeV$ (LEP II) and $\sqrt{s}=500GeV$ (NLC). The model dependence of total cross sections and kinematic distributions at these energies is shown to be weak for these three extended models, indicating that it would be difficult to establish which of them is best fit to describe the underlying new physics, should exotic leptons be detected. We suggest that, in order to resolve this difficulty, one should measure the angular distributions of single exotic leptons in longitudinally polarized $e^+e^-$ collisions. 
F. M. L. Almeida Jr, J. H. Lopes, J. A. Martins Sim\~oes, P. P.   Queiroz Filho and A. J. Ramalho