SEARCH FOR CHARGED HEAVY LEPTONS WITH ARBITRARY NEUTRINO MASSES IN e+e− ANNIHILATIONS AT $\sqrt{s} = 50 - 60.8~{\rm GeV}$

Results of a search for the pair production of charged heavy leptons in e+e− annihilations over the center-of-mass energy range of 50 to 60.8 GeV are reported. We assume that the leptons are of the sequential type but have allowed for the case where the associated neutrino might be massive. Separate searches for evidence for decays to hadronic and leptonic final states, searches specialized for the case where the charged lepton and its associated neutrino are close in mass, and a search for stable heavy leptons have uncovered no evidence for the production of such particles at these energies. Mass limits for heavy leptons and their associated neutrinos are determined for a range of hadronic and leptonic decay branching fractions. A sequential charged heavy lepton with mass between 12.6 and 29.6 GeV/c2 and with massless neutrino is excluded at the 95% confidence level.