Scientific article
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Search for flavour-changing neutral current top-quark decays t → qZ in proton-proton collisions at √s = 13 TeV with the ATLAS detector

ContributorsATLAS Collaboration
Published inJournal of High Energy Physics, vol. 1807, 176
Collection
  • Open Access - SCOAP3
Publication date2018
Abstract

A search for flavour-changing neutral-current processes in top-quark decays is presented. Data collected with the ATLAS detector from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of √s = 13 TeV, corresponding to an integrated luminosity of 36.1 fb −1 , are analysed. The search is performed using top-quark pair events, with one top quark decaying through the t → qZ ( q = u , c ) flavour-changing neutral-current channel, and the other through the dominant Standard Model mode t → bW . Only Z boson decays into charged leptons and leptonic W boson decays are considered as signal. Consequently, the final-state topology is characterized by the presence of three isolated charged leptons (electrons or muons), at least two jets, one of the jets originating from a b -quark, and missing transverse momentum from the undetected neutrino. The data are consistent with Standard Model background contributions, and at 95% confidence level the search sets observed (expected) upper limits of 1.7 × 10 −4 (2.4 × 10 −4 ) on the t → uZ branching ratio and 2.4 × 10 −4 (3.2 × 10 −4 ) on the t → cZ branching ratio, constituting the most stringent limits to date.

Keywords
  • Hadron-Hadron scattering (experiments)
Citation (ISO format)
ATLAS Collaboration. Search for flavour-changing neutral current top-quark decays t → qZ in proton-proton collisions at √s = 13 TeV with the ATLAS detector. In: Journal of High Energy Physics, 2018, vol. 1807, p. 176. doi: 10.1007/JHEP07(2018)176
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Article (Published version)
Identifiers
ISSN of the journal1029-8479
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