Combined Tevatron upper limit ongg→H→W+W−and constraints on the Higgs boson mass in fourth-generation fermion models

We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson ($H$) in the process $gg\to H\to W^{+}{W}^{-}$ in $p\overline{p}$ collisions at the Fermilab Tevatron Collider at $\sqrt{s}=1.96\mathrm{TeV}$. With $4.8{\mathrm{fb}}^{-1}$ of integrated luminosity analyzed at CDF and $5.4{\mathrm{fb}}^{-1}$ at D0, the 95% confidence level upper limit on $\sigma (gg\to H)\times \mathcal{B}(H\to W^{+}{W}^{-})$ is 1.75 pb at $m_H=120\mathrm{GeV}$, 0.38 pb at $m_H=165\mathrm{GeV}$, and 0.83 pb at $m_H=200\mathrm{GeV}$. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.