A search for heavy neutrinos that are isosinglets under the standard SU(2)(
L) gauge group is made at center-of-mass energies 130 < root s < 189 GeV wi
th the L3 detector at LEP. Such heavy neutrinos are expected in many extens
ions of the Standard Model. The starch is performed for the first generatio
n heavy singlet neutrino, N-e, through the decay mode N-e --> e + W, We set
upper limits on the mixing parameter between the heavy and light neutrino
for the heavy neutrino mass range from 80 GeV to 185 GeV. (C) 1999 Elsevier
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