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 ATLAS Collaboration

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Abstract

A search for the Standard Model Higgs boson produced in association with a top-quark pair, $$t\bar{t}H$$tt¯H, is presented. The analysis uses 20.3 fb−1 of pp collision data at $$\sqrt{s}=8{{\,\mathrm TeV}}$$s=8TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the $$H \rightarrow b\bar{b}$$H→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 $$t\bar{t}$$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 $$t\bar{t}{+}b\bar{b}$$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 $${t\bar{t}H}$$tt¯H signal cross section to the Standard Model expectation is found to be $$\mu = 1.5 \pm 1.1$$μ=1.5±1.1 assuming a Higgs boson mass of 125$${{\,\mathrm GeV\,}}$$GeV.

Original languageEnglish (US)
Article number349
JournalEuropean Physical Journal C
Volume75
Issue number7
DOIs
StatePublished - Jul 30 2015

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Engineering (miscellaneous)

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