Search for top-quark decays t → Hq with 36 fb⁻¹ of pp collision data at √s=13 TeV with the ATLAS detector

Miucci, Antonio; Merlassino, Claudia; Haug, Sigve; Weber, Michael; Anders, John Kenneth; Beck, Hans Peter; Ereditato, Antonio; Rimoldi, Marco; Weston, Thomas Daniel (2019). Search for top-quark decays t → Hq with 36 fb⁻¹ of pp collision data at √s=13 TeV with the ATLAS detector. Journal of High Energy Physics, 2019(5) Springer 10.1007/JHEP05(2019)123

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A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t → Hq, is presented. The search is based on a dataset of pp collisions at √s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→bb¯¯ and H → τ+τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t → Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 1.1 × 10−3 (8.3 × 10−4) and 1.2 × 10−3 (8.3 × 10−4), respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)
08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP)

UniBE Contributor:

Miucci, Antonio; Merlassino, Claudia; Haug, Sigve; Weber, Michael; Anders, John Kenneth; Beck, Hans Peter; Ereditato, Antonio; Rimoldi, Marco and Weston, Thomas Daniel

Subjects:

500 Science > 530 Physics

ISSN:

1029-8479

Publisher:

Springer

Language:

English

Submitter:

BORIS Import LHEP

Date Deposited:

18 Jun 2020 10:26

Last Modified:

18 Jun 2020 10:26

Publisher DOI:

10.1007/JHEP05(2019)123

Additional Information:

Kollaboration - Es sind nur die Berner Autoren namentlich erwaehnt; ATLAS collaboration

BORIS DOI:

10.7892/boris.143610

URI:

https://boris.unibe.ch/id/eprint/143610

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