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Search for flavour-changing neutral current top-quark decays to qZ in pp collision data collected with the ATLAS detector at v s =8 TeV

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posted on 2023-06-21, 06:01 authored by Benedict AllbrookeBenedict Allbrooke, Lily AsquithLily Asquith, Alessandro CerriAlessandro Cerri, C A Chavez Barajas, Antonella De SantoAntonella De Santo, C T Potter, Fabrizio SalvatoreFabrizio Salvatore, I Santoyo Castillo, K Suruliz, Mark SuttonMark Sutton, Iacopo Vivarelli, et al The ATLAS Collaboration
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 vs=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 ? ?? and H ? WW*, tt 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 |?tcH| and |?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.

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Publication status

  • Published

File Version

  • Published version

Journal

European Physical Journal C: Particles and Fields

ISSN

1434-6044

Publisher

Springer Verlag

Issue

1

Volume

76

Page range

12

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2016-06-17

First Open Access (FOA) Date

2016-06-17

First Compliant Deposit (FCD) Date

2016-06-17

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