Impact on the Higgs Production Cross Section and Decay Branching Fractions of Heavy Quarks and Leptons in a Fourth Generation Model

In a fourth generation model with heavy quarks, the production cross section of the Higgs boson in the gluon-gluon fusion process is significantly increased due to additional quark loops. In a similar way, the partial decay width of the decay channels $H\to gg,\gamma \gamma$ and $\gamma Z$ is modified. These changes and their impact on the Higgs search are discussed.