The ttH Physics Channel at the LHC

The global fit of Higgs boson contributions to the electroweak experimental observables, computed within the Standard Model, favors a light Higgs with a mass of m_H=76+33-25 GeV/c2, on the edge of the 95\% Confidence Level region excluded at LEP. Finding a light Higgs boson at LHC is experimentally difficult and several channels with various signatures will be sought for. The associate production of the Higgs boson with a pair of top quarks, with the subsequent decay of the Higgs boson into b-quark pairs (dominant for m_H<135 GeV/c2) , is one of the channels considered. This channel also gives a unique access to the top Yukawa coupling. The potential of the ATLAS and CMS detectors to observe this channel will be described. Several ingredients are crucial: reconstruction of the top-antitop system with a high-purity, excellent b-tagging capabilities and good knowledge of the ttbar+jets background. The decay of H to WW and to gamma gamma in ttH processes has been also studied and it is briefly reported.