Abstract
This is the publisher's version, also available electronically from http://link.springer.com/article/10.1007%2FJHEP05%282013%29145.
A search for the standard model Higgs boson produced in association with a top-quark pair is presented using data samples corresponding to an integrated luminosity of 5.0 fb(−1) (5.1 fb(−1)) collected in pp collisions at the center-of-mass energy of 7 TeV (8 TeV). Events are considered where the top-quark pair decays to either one lepton+jets (tt-bar→ℓνqq-bar ′bb-bar) or dileptons (tt-bar→ℓ(+)νℓ(−)ν-bar bb-bar) , ℓ being an electron or a muon. The search is optimized for the decay mode H→bb-bar . The largest background to the tt-barH signal is top-quark pair production with additional jets. Artificial neural networks are used to discriminate between signal and background events. Combining the results from the 7 TeV and 8 TeV samples, the observed (expected) limit on the cross section for Higgs boson production in association with top-quark pairs for a Higgs boson mass of 125 GeV is 5.8 (5.2) times the standard model expectation.
