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

Abraham, N L, Allbrooke, B M M, Asquith, L, Cerri, A, Chavez Barajas, C A, De Santo, A, Jones, S, Lerner, G, Miano, F, Salvatore, F, Santoyo Castillo, I, Shehu, C Y, Shaw, Kate, Stevenson, T J, Suruliz, K, Sutton, M R, Tresoldi, F, Vivarelli, I, Winkels, E, Winston, O J, The ATLAS Collaboration, and others, (2018) Search for flavour-changing neutral current top-quark decays t > qZ in proton-proton collisions at sqrt (s) = 13 TeV with the ATLAS detector. Journal of High Energy Physics, 7. p. 176. ISSN 1126-6708

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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 p s = 13TeV, corresponding to an integrated luminosity of 36.1 fb1, 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 x 10-4 (2:4 x 10-4) on the t > uZ branching ratio and 2:4 _ 104 (3:2 _ 104) on the t > cZ branching ratio, constituting the most stringent limits to date.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Experimental Particle Physics Research Group
Subjects: Q Science > QC Physics
Depositing User: Alice Jackson
Date Deposited: 08 Nov 2018 11:45
Last Modified: 12 Nov 2018 15:04
URI: http://srodev.sussex.ac.uk/id/eprint/80060

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