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Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton collisions at $\sqrt{s}=$ 13 TeV

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Alessandro Caratelli, Xin Chen, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Sebastiana Gianì, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Lei Li, Jing Li, Yiming Li, Wei Li, Zhen Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Amr Mohamed, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Jessica Prisciandaro, Quentin Python, Andrea Rizzi, Paolo Ronchese, Valérie Scheurer, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Yi Wang, Zheng Wang, Mingkui Wang, Qian Wang, Jian Wang, Siyuan Wang, Hui Wang, Xiao Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang, Yi Zhang
2019
Rapport ou document de travail

Résumé

The standard model (SM) production of four top quarks ( $\mathrm{t\bar{t}t\bar{t}}$ ) in proton-proton collision is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 fb $^{-a}$ at a center-of-mass energy of 13 TeV. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $\mathrm{t\bar{t}t\bar{t}}$ signal are respectively 2.6 and 2.7 standard deviations, and the $\mathrm{t\bar{t}t\bar{t}}$ cross section is measured to be 12.6 $^{+5.8}_{-5.2}$ fb. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $y_{\mathrm{t}}$ , yielding a limit of $|{y_{\mathrm{t}}/y_{\mathrm{t}}^{\mathrm{SM}}}|

Official source

https://infoscience.epfl.ch/record/275117?ln=fr

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Official source

https://infoscience.epfl.ch/record/275117?ln=fr

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Concepts associés (26)

Concepts associés

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Publications associées (115)

Publications associées

Chargement

Search for standard model production of four top quarks with same-sign and multilepton final states in proton–proton collisions at $\sqrt{s} = 13\,\text {TeV} $

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Michele Bianco, Roberto Castello, Xin Chen, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Alessandro Degano, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Donghyun Kim, Ji Hyun Kim, Sanjeev Kumar, Vineet Kumar, Ajay Kumar, Ekaterina Kuznetsova, Ho Ling Li, Jing Li, Wei Li, Shuai Liu, Zhen Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Varun Sharma, Ashish Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Gurpreet Singh, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Mingkui Wang, Jian Wang, Hui Wang, Qian Wang, Zheng Wang, Yi Wang, Siyuan Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Wenjing Wu, Fan Xia, Meng Xiao, Zhirui Xu, Yong Yang, Kai Yi

A search for standard model production of four top quarks (

\mathrm {t}\overline{\mathrm {t}} \mathrm {t}\overline{\mathrm {t}}

) is reported using events containing at least three leptons (

\mathrm {e}, \mathrm {\mu }

) or a same-sign lepton pair. The events are produced in proton–proton collisions at a center-of-mass energy of 13

\,\text {TeV}

at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9

\,\text {fb}^{-1}

. Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the

\mathrm {t}\overline{\mathrm {t}} \mathrm {t}\overline{\mathrm {t}}

cross section is measured to be

16.9^{+13.8-11.4}

\,\text {fb}

, in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level.

2018

Measurement of Top Quark-Antiquark Pair Production in Association with a W or Z Boson in pp Collisions at $\sqrt{s} = 8$ $\,\text {TeV}$

Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Giovanni Bianchi, Roberto Castello, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Yifei Guo, Ruchi Gupta, Csaba Hajdu, Alexis Kalogeropoulos, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Shuai Liu, Hao Liu, Werner Lustermann, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Wei Sun, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Zheng Wang, Xiao Wang, Jian Wang, Qian Wang, Matthias Weber, Matthias Wolf, Fan Yang, Yong Yang, Kai Yi, Lei Zhang, Yu Zheng

A measurement of the cross section for the production of top quark–antiquark pairs (

{\mathrm {t}}\overline{{\mathrm {t}}}

) in association with a vector boson V (W or Z) in proton-proton collisions at

\sqrt{s} = 8

\,\text {TeV}

is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb

^{-1}

recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and

\mu

) channels: a same-sign dilepton analysis targeting

{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}

events, and trilepton and four-lepton analyses designed for

{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}

events. In the same-sign dilepton channel, the

{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}

cross section is measured as

\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}} = 170 ^{+90-80}\,\text {(stat)} \pm 70\,\text {(syst)} \, \text {fb}

, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the

{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}

cross section,

\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}} = 200 ^{+80-70}\,\text {(stat)} ^{+40-30}\,\text {(syst)} \mathrm{fb}^{-1}

, is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive

{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {V}}

process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

2014

Search for the associated production of a Higgs boson with a single top quark in proton-proton collisions at $ \sqrt{s}=8 $ TeV

Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Roberto Castello, Juan Ramon Castiñeiras De Saa, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Csaba Hajdu, Peter Hansen, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Shuai Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Xin Sun, Wei Sun, Marco Trovato, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Qian Wang, Yi Wang, Siyuan Wang, Zheng Wang, Jian Wang, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Fan Yang, Yong Yang, Kai Yi

This paper presents the search for the production of a Higgs boson in association with a single top quark (tHq), using data collected in proton-proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb

^{−1}

. The search exploits a variety of Higgs boson decay modes resulting in final states with photons, bottom quarks, and multiple charged leptons, including tau leptons, and employs a variety of multivariate techniques to maximize sensitivity to the signal. The analysis is optimized for the opposite sign of the Yukawa coupling to that in the standard model, corresponding to a large enhancement of the signal cross section. In the absence of an excess of candidate signal events over the background predictions, 95% confidence level observed (expected) upper limits on anomalous tHq production are set, ranging between 600 (450) fb and 1000 (700) fb depending on the assumed diphoton branching fraction of the Higgs boson. This is the first time that results on anomalous tHq production have been reported.

2016