Revisiting constraints on fourth generation neutrino masses

Abstract

We revisit the current experimental bounds on fourth generation Majorana neutrino masses, including the effects of right-handed neutrinos. Current bounds from LEP II are significantly altered by a global analysis. We show that the current bounds on fourth generation neutrinos decaying to $eW$ or $\ensuremath{\mu}W$ can be reduced to about 80 GeV (from the current bound of 90 GeV), while a neutrino decaying to $\ensuremath{\tau}W$ can be as light as 62.1 GeV. The weakened bound opens up a neutrino decay channel for intermediate mass Higgs, and interesting multiparticle final states for Higgs and fourth generation lepton decays.