M. Acciarri et al., Search for heavy neutral and charged leptons in e(+)e(-) annihilation at root s=183 and 189 GeV, PHYS LETT B, 462(3-4), 1999, pp. 354-364
A search for unstable neutral and charged heavy leptons as well as for stab
le charged heavy leptons is performed at center-of-mass energies root s = 1
83 and 189 GeV with the L3 detector at LEP. No evidence for their existence
is found. We exclude neutral heavy leptons which couple to the electron, m
uon or tau family, of the Dirac type for masses below 92.4, 93.3 and 83.3 G
eV, and of the Majorana type for masses below 81.8, 84.1 and 73.5 GeV, resp
ectively. We exclude unstable charged heavy leptons for masses below 93.9 G
eV for a wide range of the associated neutral heavy lepton mass. If the uns
table charged heavy lepton decays to a light neutrino, we exclude masses be
low 92.4 GeV. The production of stable charged heavy leptons with moss less
than 93.5 GeV is also excluded. (C) 1999 Published by Elsevier Science B.V
. All rights reserved.