Joint analysis of Higgs boson decays and electroweak precision observables in the standard model with a sequential fourth generation

We analyze the impact of LHC and Tevatron Higgs data on the viability of the standard model with a sequential fourth generation, assuming Dirac neutrinos and a Higgs mass of 125 GeV. To this end we perform a combined fit to the signal cross sections of pp→H→γγ, ZZ*, WW* at the LHC, to pp̄→VH→Vbb̄ ($V=W$, Z) at the Tevatron and to the electroweak precision observables. Fixing the mass of the fourth-generation down-type quark b^' to 600 GeV we find best-fit values of m_t^'=632 GeV, m_l₄=113.6 GeV and m_ν₄=58.0 GeV for the other fourth-generation fermion masses. We compare the χ² values and pulls of the different observables in the three- and four-generation case and show that the data is better described by the three-generation standard model. We also investigate the effects of mixing between the third- and fourth-generation quarks and of a future increased lower bound on the fourth-generation charged lepton mass of 250 GeV.