Light Higgs Boson Signal at LHC in the Reactions $pp \to \gamma\gamma$+Jet and $pp \to \gamma\gamma+lepton$

We discuss the SM Higgs discovery potential of the LHC in the channels pp -> H+jet -> gamma+gamma+jet and pp -> H+W/H+t+tbar -> gamma+gamma+lepton when the jet or lepton is observed at sufficiently high Pt and a small rapidity to be reliably identified. We calculate all the signal subprocesses and the irreducible background with realistic kinematical cuts. The reducible QCD background is also estimated. We conclude that the channel gamma+gamma+jet can give about 120-200 signal events for Higgs mass MH=100-140 GeV at the integrated luminosity of 30 inverse fb. This signal rate should be compared with only 330-600 events for the irreducible background per two-photon invariant mass interval of 2 GeV. We estimate the QCD reducible background at the level of 20% of the irreducible one. Thus, one may hope that the Higgs boson can be discovered already after 1-1.5 years003084132 595 L. D. Bouvet, V. Chorowicz, D. Contardo, R. Haroutunian, L. Mirabito, G. Smadja, IPN Lyon, France