Higgs Decays to Unstable Neutrinos: Collider Constraints from Inclusive   Like-Sign Dilepton Searches
  We study the pair production of fourth generation neutrinos from the decay of an on-shell Higgs produced by gluon fusion. In a fourth generation scenario, the Higgs branching fraction into fourth generation neutrinos may be quite large. In the case that the unstable heavy neutrinos are a mixed Majorana and Dirac state, neutrinos pair-produced from Higgs decay will yield a substantial number of like-sign dilepton events. In this article we use inclusive like-sign dilepton searches from hadron colliders to constrain the theoretical parameter space of fourth generation leptons. 
Linda M. Carpenter and Daniel Whiteson
hep-ph