Search for fourth generation quarks and leptons at the Fermilab Tevatron and CERN large hadron collider - art. no. 095001

If the next generations of heavy quarks and leptons exist within the standa rd model (SM), they can manifest themselves in Higgs boson production at th e Fermilab Tevatron and the CERN LHC, before being actually observed. This generation leads to an increase of the Higgs boson production cross section via gluon fusion at hadron colliders by a factor 6-9. So, the study of thi s process at the Tevatron and LHC can finally fix the number of generations in the SM. Using the WW* Higgs boson decay channel, the studies at the upg raded Tevatron will answer the question about the next generation for mass values 135 GeV less than or similar to M-H less than or similar to 190 GeV. Studying the tau<(tau)over bar> channel we show its large potential for th e study of the Higgs boson at the LHC even in the standard case of three ge nerations. At the Tevatron, studies in this channel could explore the mass range 110-140 GeV. [S0556-2821(99)08319-8].