Search for Next Generations of Quarks and Leptons at the Tevatron and LHC

If next heavy generations of quarks and leptons (with heavy neutrinos) within the Standard Model exist, they can be observed in experiments with Higgs boson production at the Tevatron and LHC before the discovery of these heavy fermions. For the case of one additional generation, the cross section of the Higgs boson production via gluon fusion at hadron colliders increases by a factor $6\div 9$. So, the study of this process at the Tevatron and LHC can finally fix the number of generations in the SM.