Constraints on a Fourth Generation of Fermions from Higgs Boson Searches
Higgs branching ratios in dependence of the mass of the fourth neutrino for a Higgs mass of 125 GeV. Below GeV the new invisible decay channel opens and all other branching ratios will be strongly suppressed. This plot was, however, created with an approximate NLO expression for . The full expression will give a further suppression of the two-photon channel by a factor of about six. Figure taken from .