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

Rimoldi, Marco; Mullier, Geoffrey; Miucci, Antonio; Merlassino, Claudia; Haug, Sigve; Weber, Michael; Meloni, Federico; Beck, Hans Peter; Ereditato, Antonio (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) Springer 10.1007/JHEP07(2018)176

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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 topquark 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 x 10⁻⁴ (3.2 x 10⁻⁴) on the t → cZ branching ratio, constituting the most stringent limits to date.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP)

UniBE Contributor:

Haug, Sigve; Weber, Michael and Beck, Hans Peter

Subjects:

500 Science > 530 Physics

ISSN:

1029-8479

Publisher:

Springer

Language:

English

Submitter:

BORIS Import LHEP

Date Deposited:

25 Jun 2019 13:05

Last Modified:

23 Oct 2019 07:58

Publisher DOI:

10.1007/JHEP07(2018)176

ArXiv ID:

1803.09923

Additional Information:

Kollaboration - Es sind nur die Berner Autoren namentlich erwaehnt

BORIS DOI:

10.7892/boris.129064

URI:

https://boris.unibe.ch/id/eprint/129064

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