Search for heavy isosinglet neutrinos in e+e− annihilation at 130<s<189 GeV

Abstract A search for heavy neutrinos that are isosinglets under the standard SU (2) L gauge group is made at center-of-mass energies 130 s GeV with the L3 detector at LEP. Such heavy neutrinos are expected in many extensions of the Standard Model. The search is performed for the first generation 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.