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

The ATLAS collaboration

doi:10.1007/JHEP07(2018)176

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

The ATLAS collaboration

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

46 Scopus citations

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.[Figure not available: see fulltext.].

Original language	English
Article number	176
Journal	Journal of High Energy Physics
Volume	2018
Issue number	7
DOIs	https://doi.org/10.1007/JHEP07(2018)176
State	Published - 1 Jul 2018

Funding

Funders	Funder number
Not added	ST/L006162/1, ST/N000447/1, ST/J004804/1, ST/M000753/1, ST/N000307/1, ST/L003449/1, ST/K001329/1, ST/N000420/1
CEA-DRF
Cantons of Bern and Geneva
Czech Republic
DNSRC	IN2P3-CNRS
IRFU
In-vestissements d’Avenir Labex
MES of Russia
MESTD
MNE
MSMT
MSSR
Marie Sklo dowska-Curie Actions
RGC
Région Auvergne
Thales and Aristeia
VSC CR
Wallenberg Foundation
National Science Foundation	1812377, 1624739
U.S. Department of Energy
Alexander von Humboldt-Stiftung
CRC Health Group
Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS)
Ontario Innovation Trust
Canarie
Arizona-Nevada Academy of Science
CERN
Compute Canada
Natural Sciences and Engineering Research Council of Canada
National Research Council Canada
Canada Council for the Arts
Canada Foundation for Innovation
Science and Technology Facilities Council	ST/J005533/1
European Commission
European Research Council
Australian Research Council
Neurosurgical Research Foundation
Department of Science and Technology, Ministry of Science and Technology, India
Singapore Eye Research Institute
Helmholtz-Gemeinschaft
Deutsche Forschungsgemeinschaft
Agence Nationale de la Recherche
Japan Society for the Promotion of Science
Ministry of Education, Culture, Sports, Science and Technology
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Danmarks Grundforskningsfond
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Natural Science Foundation of China
Fundação para a Ciência e a Tecnologia
Bundesministerium für Bildung und Forschung
Chinese Academy of Sciences
Austrian Science Fund
Comisión Nacional de Investigación Científica y Tecnológica
Agencia Nacional de Promoción Científica y Tecnológica
Fonds Québécois de la Recherche sur la Nature et les Technologies
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Ministerio de Economía y Competitividad
Bundesministerium für Wissenschaft, Forschung und Wirtschaft
General Secretariat for Research and Technology
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Joint Institute for Nuclear Research
Nella and Leon Benoziyo Center for Neurological Diseases, Weizmann Institute of Science
Israel Science Foundation
Instituto Nazionale di Fisica Nucleare
Narodowe Centrum Nauki
Javna Agencija za Raziskovalno Dejavnost RS
Ministerstwo Nauki i Szkolnictwa Wyższego
Ministry of Science and Technology, Taiwan
Israeli Centers for Research Excellence
Centre National pour la Recherche Scientifique et Technique
Horizon 2020
British Columbia Knowledge Development Fund
European Regional Development Fund
Council on grants of the President of the Russian Federation
Fondation Partager le Savoir
National Research Center "Kurchatov Institute"
Institutul de Fizică Atomică

Keywords

Hadron-Hadron scattering (experiments)

Access to Document

10.1007/JHEP07(2018)176

Cite this

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

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.[Figure not available: see fulltext.].",

keywords = "Hadron-Hadron scattering (experiments)",

author = "{The ATLAS collaboration} and M. Aaboud and G. Aad and B. Abbott and O. Abdinov and B. Abeloos and Abidi, {S. H.} and AbouZeid, {O. S.} and Abraham, {N. L.} and H. Abramowicz and H. Abreu and Y. Abulaiti and Acharya, {B. S.} and S. Adachi and L. Adamczyk and J. Adelman and M. Adersberger and T. Adye and Affolder, {A. A.} and Y. Afik and C. Agheorghiesei and Aguilar-Saavedra, {J. A.} and F. Ahmadov and G. Aielli and S. Akatsuka and H. Akerstedt and {\AA}kesson, {T. P.A.} and E. Akilli and Akimov, {A. V.} and Alberghi, {G. L.} and J. Albert and P. Albicocco and {Alconada Verzini}, {M. J.} and S. Alderweireldt and M. Aleksa and Aleksandrov, {I. N.} and C. Alexa and G. Alexander and T. Alexopoulos and M. Alhroob and A. Ashkenazi and L. Barak and G. Bella and Y. Benhammou and T. Cao and E. Etzion and O. Kuprash and Lutz, {M. S.} and Y. Oren and M. Pitt and A. Soffer",

note = "Publisher Copyright: {\textcopyright} 2018, The Author(s).",

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AU - The ATLAS collaboration

AU - Aaboud, M.

AU - Aad, G.

AU - Abbott, B.

AU - Abdinov, O.

AU - Abeloos, B.

AU - Abidi, S. H.

AU - AbouZeid, O. S.

AU - Abraham, N. L.

AU - Abramowicz, H.

AU - Abreu, H.

AU - Abulaiti, Y.

AU - Acharya, B. S.

AU - Adachi, S.

AU - Adamczyk, L.

AU - Adelman, J.

AU - Adersberger, M.

AU - Adye, T.

AU - Affolder, A. A.

AU - Afik, Y.

AU - Agheorghiesei, C.

AU - Aguilar-Saavedra, J. A.

AU - Ahmadov, F.

AU - Aielli, G.

AU - Akatsuka, S.

AU - Akerstedt, H.

AU - Åkesson, T. P.A.

AU - Akilli, E.

AU - Akimov, A. V.

AU - Alberghi, G. L.

AU - Albert, J.

AU - Albicocco, P.

AU - Alconada Verzini, M. J.

AU - Alderweireldt, S.

AU - Aleksa, M.

AU - Aleksandrov, I. N.

AU - Alexa, C.

AU - Alexander, G.

AU - Alexopoulos, T.

AU - Alhroob, M.

AU - Ashkenazi, A.

AU - Barak, L.

AU - Bella, G.

AU - Benhammou, Y.

AU - Cao, T.

AU - Etzion, E.

AU - Kuprash, O.

AU - Lutz, M. S.

AU - Oren, Y.

AU - Pitt, M.

AU - Soffer, A.

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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.[Figure not available: see fulltext.].

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.[Figure not available: see fulltext.].

KW - Hadron-Hadron scattering (experiments)

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JO - Journal of High Energy Physics

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ER -

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

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Keywords

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