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

Barton, Adam Edward and Beattie, Michael and Bertram, Iain Alexander and Borissov, Guennadi and Bouhova-Thacker, Evelina Vassileva and Fox, Harald and Henderson, Robert Charles William and Jones, Roger William Lewis and Kartvelishvili, Vakhtang and Long, Robin Eamonn and Love, Peter Allan and Muenstermann, Daniel Matthias Alfred and Parker, Adam Jackson and Skinner, Malcolm and Smizanska, Maria and Walder, James William and Wharton, Andrew Mark and Whitmore, Ben (2018) Search for flavour-changing neutral current top-quark decays t→qZ in proton-proton collisions at √s=13 TeV with the ATLAS detector. Journal of High Energy Physics, 2018 (7). ISSN 1029-8479

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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.

Item Type:
Journal Article
Journal or Publication Title:
Journal of High Energy Physics
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/3100/3106
Subjects:
ID Code:
128034
Deposited By:
Deposited On:
04 Oct 2018 15:26
Refereed?:
Yes
Published?:
Published
Last Modified:
24 Mar 2020 08:04