Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector

Aad, G. and Abbott, B. and Abdallah, J. and Abdinov, O. and Aben, R. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2015) Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector. PHYSICS LETTERS B, 749. pp. 519-541. ISSN 0370-2693

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Abstract

A search for the associated production of the Higgs boson with a top quark pair is performed in multilepton final states using 20.3 fb−1 of proton–proton collision data recorded by the ATLAS experi- ment at √s = 8 TeV at the Large Hadron Collider. Five final states, targeting the decays H → WW∗, ττ, and ZZ∗, are examined for the presence of the Standard Model (SM) Higgs boson: two same-charge light leptons (e or μ) without a hadronically decaying τ lepton; three light leptons; two same-charge light leptons with a hadronically decaying τ lepton; four light leptons; and one light lepton and two hadronically decaying τ leptons. No significant excess of events is observed above the background expectation. The best fit for the t¯tH production cross section, assuming a Higgs boson mass of 125 GeV, is 2.1+1.4 −1.2 times the SM expectation, and the observed (expected) upper limit at the 95% confidence level is 4.7 (2.4) times the SM rate. The p-value for compatibility with the background-only hypothesis is 1.8σ; the expectation in the presence of a Standard Model signal is 0.9σ.

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