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Type: Journal article
Title: Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector
Other Titles: Search for flavour-changing neutral current top quark decays t -> Hq in pp collisions at root s=8 TeV with the ATLAS detector
Author: The, A.C.
Aad, G.
Abbott, B.
Abdallah, J.
Abdinov, O.
Aben, R.
Abolins, M.
AbouZeid, O.
Abramowicz, H.
Abreu, H.
Abreu, R.
Abulaiti, Y.
Acharya, B.
Adamczyk, L.
Adams, D.
Adelman, J.
Adomeit, S.
Adye, T.
Affolder, A.
Agatonovic-Jovin, T.
et al.
Citation: Journal of High Energy Physics, 2015; 2015(12):061-1-061-65
Publisher: Springer
Issue Date: 2015
ISSN: 1126-6708
Statement of
G. Aad ... P. Jackson … L. Lee … A. Petridis … N. Soni … M.J. White … et al. (ATLAS Collaboration)
Abstract: A search for flavour-changing neutral current decays of a top quark to an uptype quark (q = u, c) and the Standard Model Higgs boson, where the Higgs boson decays to bb¯¯, is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at s√=8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by tt¯→WbWb decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the t → Hc and t → Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H → γγ and H → WW *, ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the |λ tcH | and |λ tuH | couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far.
Keywords: Hadron-Hadron Scattering; Top Physics; Higgs Physics; FCNC Interactions
Rights: © The Author(s) 2015. This article is published under an open access license. Please check the 'Copyright Information' section for details of this license and what re-use is permitted. If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and re-use information, please contact the Rights and Permissions team.
RMID: 0030041011
DOI: 10.1007/JHEP12(2015)061
Appears in Collections:Physics publications

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