Abstract
A search for the Standard Model Higgs boson produced in association with a top-quark pair, tbar{t}H, is presented. The analysis uses 20.3 fb−1 of pp collision data at sqrt{s}=8{{,mathrm TeV}}, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the H rightarrow bbar{b} 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 tbar{t}+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 tbar{t}{+}bbar{b} 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 {tbar{t}H} signal cross section to the Standard Model expectation is found to be mu = 1.5 pm 1.1 assuming a Higgs boson mass of 125{{,mathrm GeV,}}.
Highlights
This paper describes a search for the Standard Model (SM) Higgs boson in the ttH production mode and is designed to be primarily sensitive to the H → bbdecay, other Higgs boson decay modes are treated as signal
The analysis focuses on final states containing one or two electrons or muons from the decay of the ttsystem, referred to as the single-lepton and dilepton channels, respectively
A search has been performed for the Standard Model Higgs ubsoisnogn2p0r.o3dfubc−e1doifnpapsscooclliiastiioonndwatiathata√tosp=-qu8aTrkeVpaciorll(etcttHed) with the ATLAS detector during the first run of the Large Hadron Collider
Summary
This paper describes a search for the SM Higgs boson in the ttH production mode and is designed to be primarily sensitive to the H → bbdecay, other Higgs boson decay modes are treated as signal. A search for the associated production of the Higgs boson with a top-quark pair using several Higgs decay modes (including H → bb) has recently been published by the CMS Collaboration [24] quoting a ratio of the measured ttH signal cross section to the SM expectation for a Higgs boson mass of 125.6 GeV of μ = 2.8 ± 1.0. The main source of background to this search comes from top-quark pairs produced in association with additional jets. A second contribution arises from ttproduction in association with light-quark (u, d, s) or gluon jets, referred
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
