TY - JOUR

T1 - Search for flavour-changing neutral current top-quark decays t→qZ in proton-proton collisions at √s=13 TeV with the ATLAS detector

AU - Barton, Adam Edward

AU - Beattie, Michael

AU - Bertram, Iain Alexander

AU - Borissov, Guennadi

AU - Bouhova-Thacker, Evelina Vassileva

AU - Fox, Harald

AU - Henderson, Robert Charles William

AU - Jones, Roger William Lewis

AU - Kartvelishvili, Vakhtang

AU - Long, Robin Eamonn

AU - Love, Peter Allan

AU - Muenstermann, Daniel Matthias Alfred

AU - Parker, Adam Jackson

AU - Skinner, Malcolm

AU - Smizanska, Maria

AU - Walder, James William

AU - Wharton, Andrew Mark

AU - Whitmore, Ben

AU - The ATLAS collaboration

PY - 2018/7/31

Y1 - 2018/7/31

N2 - 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.

AB - 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.

U2 - 10.1007/JHEP07(2018)176

DO - 10.1007/JHEP07(2018)176

M3 - Journal article

VL - 2018

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

SN - 1029-8479

IS - 7

M1 - 176

ER -