Revisiting Constraints on Fourth Generation Neutrino Masses

TL;DR

This paper reevaluates experimental limits on fourth-generation Majorana neutrino masses, revealing that current bounds can be lower than previously thought, which impacts Higgs decay channels and collider phenomenology.

Contribution

It provides a comprehensive global analysis that revises the bounds on fourth-generation neutrino masses, considering right-handed neutrinos and decay channels.

Findings

Bounds on eW and muW neutrinos reduced to ~80 GeV

Tau W neutrino can be as light as 62.1 GeV

Implications for Higgs decay channels and collider signatures

Abstract

We revisit the current experimental bounds on fourth-generation Majorana neutrino masses, including the effects of right handed neutrinos. Current bounds from LEPII are significantly altered by a global analysis. We show that the current bounds on fourth generation neutrinos decaying to eW and mu W can be reduced to about 80 GeV (from the current bound of 90 GeV), while a neutrino decaying to 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 multi-particle final states for Higgs and fourth generation lepton decays.