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

M. Aaboud; G. Aad; B. Abbott; O. Abdinov; B Abeloos; S.H. Abidi; Ossama Sherif Alexander Abouzeid; NL Abraham; H. Abramowicz; H. Abreu; Y. Abulaiti; B.S. Acharya; Sosuke Adachi; L. Adamczyk; J. Adelman; M. Adersberger; T. Adye; A. A. Affolder; Y.  Afik; C. Agheorghiesei; J. A. Aguilar-Saavedra; F. Ahmadov; Alejandro Alonso Diaz; Geert-Jan Besjes; Milena Bajic; Flavia de Almeida Dias; Mogens Dam; Gorm Aske Gram Krohn Galster; Jørn Dines Hansen; Jørgen Beck Hansen; Peter Henrik Hansen; James William Monk; Troels Christian Petersen; Simon Holm Stark; Fabian Alexander Jürgen Thiele; Graig Wiglesworth; Stefania Xella

doi:10.1007/JHEP07(2018)176

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

M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B Abeloos, S.H. Abidi, Ossama Sherif Alexander Abouzeid, NL Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B.S. Acharya, Sosuke Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, C. AgheorghieseiJ. A. Aguilar-Saavedra, F. Ahmadov, Alejandro Alonso Diaz, Geert-Jan Besjes, Milena Bajic, Flavia de Almeida Dias, Mogens Dam, Gorm Aske Gram Krohn Galster, Jørn Dines Hansen, Jørgen Beck Hansen, Peter Henrik Hansen, James William Monk, Troels Christian Petersen, Simon Holm Stark, Fabian Alexander Jürgen Thiele, Graig Wiglesworth, Stefania Xella

Experimental Particle Physics

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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.[Figure not available: see fulltext.].

Original language	English
Article number	176
Journal	The Journal of High Energy Physics
Volume	2018
Issue number	7
Number of pages	41
ISSN	1126-6708
DOIs	https://doi.org/10.1007/JHEP07(2018)176
Publication status	Published - 1 Jul 2018

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Aaboud, M., Aad, G., Abbott, B., Abdinov, O., Abeloos, B., Abidi, S. H., Abouzeid, O. S. A., Abraham, NL., Abramowicz, H., Abreu, H., Abulaiti, Y., Acharya, B. S., Adachi, S., Adamczyk, L., Adelman, J., Adersberger, M., Adye, T., Affolder, A. A., Afik, Y., ... Xella, S. (2018). Search for flavour-changing neutral current top-quark decays t -> qZ in proton-proton collisions at root s=13 TeV with the ATLAS detector. The Journal of High Energy Physics, 2018(7), Article 176. https://doi.org/10.1007/JHEP07(2018)176

Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abidi, SH, Abouzeid, OSA, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adamczyk, L, Adelman, J, Adersberger, M, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Alonso Diaz, A, Besjes, G-J, Bajic, M, de Almeida Dias, F, Dam, M, Galster, GAGK, Hansen, JD , Hansen, JB , Hansen, PH, Monk, JW, Petersen, TC, Stark, SH, Thiele, FAJ, Wiglesworth, G & Xella, S 2018, 'Search for flavour-changing neutral current top-quark decays t -> qZ in proton-proton collisions at root s=13 TeV with the ATLAS detector', The Journal of High Energy Physics, vol. 2018, no. 7, 176. https://doi.org/10.1007/JHEP07(2018)176

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title = "Search for flavour-changing neutral current top-quark decays t -> qZ in proton-proton collisions at root 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.].",

author = "M. Aaboud and G. Aad and B. Abbott and O. Abdinov and B Abeloos and S.H. Abidi and Abouzeid, {Ossama Sherif Alexander} and NL Abraham and H. Abramowicz and H. Abreu and Y. Abulaiti and B.S. Acharya and Sosuke 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 {Alonso Diaz}, Alejandro and Geert-Jan Besjes and Milena Bajic and {de Almeida Dias}, Flavia and Mogens Dam and Galster, {Gorm Aske Gram Krohn} and Hansen, {J{\o}rn Dines} and Hansen, {J{\o}rgen Beck} and Hansen, {Peter Henrik} and Monk, {James William} and Petersen, {Troels Christian} and Stark, {Simon Holm} and Thiele, {Fabian Alexander J{\"u}rgen} and Graig Wiglesworth and Stefania Xella",

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

AU - Aaboud, M.

AU - Aad, G.

AU - Abbott, B.

AU - Abdinov, O.

AU - Abeloos, B

AU - Abidi, S.H.

AU - Abouzeid, Ossama Sherif Alexander

AU - Abraham, NL

AU - Abramowicz, H.

AU - Abreu, H.

AU - Abulaiti, Y.

AU - Acharya, B.S.

AU - Adachi, Sosuke

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 - Alonso Diaz, Alejandro

AU - Besjes, Geert-Jan

AU - Bajic, Milena

AU - de Almeida Dias, Flavia

AU - Dam, Mogens

AU - Galster, Gorm Aske Gram Krohn

AU - Hansen, Jørn Dines

AU - Hansen, Jørgen Beck

AU - Hansen, Peter Henrik

AU - Monk, James William

AU - Petersen, Troels Christian

AU - Stark, Simon Holm

AU - Thiele, Fabian Alexander Jürgen

AU - Wiglesworth, Graig

AU - Xella, Stefania

PY - 2018/7/1

Y1 - 2018/7/1

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.].

U2 - 10.1007/JHEP07(2018)176

DO - 10.1007/JHEP07(2018)176

M3 - Journal article

SN - 1126-6708

VL - 2018

JO - The Journal of High Energy Physics

JF - The Journal of High Energy Physics

IS - 7

M1 - 176

ER -

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

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