M. Acciarri et al., SEARCH FOR HEAVY NEUTRAL AND CHARGED LEPTONS IN E(-) ANNIHILATION AT ROOT-S=161 AND ROOT-S=172 GEV()E(), Physics letters. Section B, 412(1-2), 1997, pp. 189-200
A search for unstable neutral and charged heavy leptons as well as for
stable charged heavy leptons has been made at center-of-mass energies
root s = 161 GeV and root s = 172 GeV with the L3 detector at LEP. No
evidence for their existence was found. We exclude unstable neutral l
eptons of Dirac (Majorana) type for masses below 78.0 (66.7), 78.0 (66
.7) and 72.2 (58.2) GeV, if the heavy neutrino couples to the electron
, muon or tau family, respectively. We exclude unstable charged heavy
leptons for masses below 81.0 GeV for a wide mass range of the associa
ted neutral heavy lepton. The production of stable charged heavy lepto
ns with a mass less than 84.2 GeV is also excluded. If the unstable ch
arged heavy lepton decays via mixing into a massless neutrino, we excl
ude masses below 78.7 GeV. (C) 1997 Elsevier Science B.V.