Clark, Brian LeeFranklin, MelissaHuth, JohnIppolito, ValerioLopez Mateos, DavidMercurio, KevinMorii, MasahiroSkottowe, Hugh PhilipSpearman, WilliamSun, SiyuanTolley, EmmaYen, Andy2017-07-182015Aad, G., B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, et al. 2015. “ Search for the Standard Model Higgs boson produced in association with top quarks and decaying into bb¯ in pp collisions at s√ = 8 TeV with the ATLAS detector.” The European Physical Journal C 75 (7) (July). doi:10.1140/epjc/s10052-015-3543-1.1434-6044http://nrs.harvard.edu/urn-3:HUL.InstRepos:33464183A search for the Standard Model Higgs boson produced in association with a pair of top quarks, tt¯H, is presented. The analysis uses 20.3 fb−1 of pp collision data at s√ = 8 TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the H to bb¯ decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by tt¯+jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible tt¯+bb¯ background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95% confidence level. The ratio of the measured tt¯H signal cross section to the Standard Model expectation is found to be μ = 1.5 ± 1.1 assuming a Higgs boson mass of 125 GeV.en-USJournal Article2017-07-1810.1140/epjc/s10052-015-3543-1