We consider the impact of a 4th generation on Higgs to γγ and WW,ZZ signals and demonstrate that the Tevatron and LHC have essentially eliminated the possibility of a 4th generation if the Higgs is SM-like and has mass below 200 GeV. We also show that the absence of enhanced Higgs signals in current data sets in the γγ and WW,ZZ final states can strongly constrain the possibility of a 4th generation in two-Higgs-doublet models of type II, including the MSSM.
@article{arxiv.1105.3965,
title = {Ruling out a 4th generation using limits on hadron collider Higgs signals},
author = {John F. Gunion},
journal= {arXiv preprint arXiv:1105.3965},
year = {2011}
}