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Search for pair-produced vectorlike B quarks in proton-proton collisions at $\sqrt{s}$=8 TeV

Muhammad Ahmad, Ahmed Ali, Christian Amstutz, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Giovanni Bianchi, Roberto Castello, Juan Ramon Castiñeiras De Saa, Yixing Chen, Tian Cheng, 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, Ho Ling Li, Wei Li, Shuai Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Wei Sun, Marco Trovato, Andromachi Tsirou, Paul Turner, Joao Varela, Zheng Wang, Jian Wang, Rui Wang, Siyuan Wang, Qian Wang, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Yong Yang, Fan Yang, Kai Yi, Hang Yin
2016
Article

Résumé

A search for the production of a heavy B quark, having electric charge -1/3 and vector couplings to W, Z, and H bosons, is carried out using proton-proton collision data recorded at the CERN LHC by the CMS experiment, corresponding to an integrated luminosity of 19.7 fb−1. The B quark is assumed to be pair produced and to decay in one of three ways: to tW, bZ, or bH. The search is carried out in final states with one, two, and more than two charged leptons, as well as in fully hadronic final states. Each of the channels in the exclusive final-state topologies is designed to be sensitive to specific combinations of the B quark-antiquark pair decays. The observed event yields are found to be consistent with the standard model expectations in all the final states studied. A statistical combination of these results is performed, and upper limits are set on the cross section of the strongly produced B quark-antiquark pairs as a function of the B quark mass. Lower limits on the B quark mass between 740 and 900 GeV are set at a 95% confidence level, depending on the values of the branching fractions of the B quark to tW, bZ, and bH. Overall, these limits are the most stringent to date.

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https://infoscience.epfl.ch/record/274683?ln=fr

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Publications associées (120)

Search for the production of an excited bottom quark decaying to $tW$ 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, 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, Amr Mohamed, 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, Marco Trovato, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Qian Wang, Zheng Wang, Jian Wang, Siyuan Wang, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Fan Yang, Yong Yang, Kai Yi, Hang Yin

A search is presented for a singly produced excited bottom quark (b

^{*}

) decaying to a top quark and a W boson in the all-hadronic, lepton+jets, and dilepton final states in proton-proton collisions at

\sqrt{s}=8

TeV recorded by the CMS experiment at the CERN LHC. Data corresponding to an integrated luminosity of 19.7 fb

^{−1}

are used. No significant excess of events is observed with respect to standard model expectations. We set limits at 95% confidence on the product of the b

^{*}

quark production cross section and its branching fraction to tW. The cross section limits are interpreted for scenarios including left-handed, right-handed, and vector-like couplings of the b

^{*}

quark and are presented in the two-dimensional coupling plane based on the production and decay coupling constants. The masses of the left-handed, right-handed, and vector-like b

^{*}

quark states are excluded at 95% confidence below 1390, 1430, and 1530 GeV, respectively, for benchmark couplings. This analysis gives the most stringent limits on the mass of the b

^{∗}

quark to date.

2016

Chargement

Search for neutral color-octet weak-triplet scalar particles in proton-proton collisions at $ \sqrt{s}=8 $ TeV

Muhammad Ahmad, Ahmed Ali, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Giovanni Bianchi, Roberto Castello, Juan Ramon Castiñeiras De Saa, Yixing Chen, Tian Cheng, 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, Sanjeev Kumar, Ajay Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Hao Liu, Shuai Liu, Werner Lustermann, Bibhuprasad Mahakud, 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, Marco Trovato, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Siyuan Wang, Qian Wang, Zheng Wang, Jian Wang, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Fan Yang, Yong Yang, Kai Yi, Hang Yin

A search for pair production of neutral color-octet weak-triplet scalar particles (Θ

^{0}

) is performed in processes where one Θ

^{0}

decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons. The search is performed with data collected by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 19.7 fb

^{−1}

of proton-proton collisions at

\sqrt{s}=8

TeV. The number of observed events is found to be in agreement with the standard model predictions. The 95% confidence level upper limit on the product of the cross section and branching fraction is obtained as a function of the Θ

^{0}

mass. The 95% confidence level lower bounds on the Θ

^{0}

mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model.

2015

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Search for anomalous production of events with three or more leptons in $pp$ collisions at $\sqrt(s) =$ 8 TeV

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

A search for physics beyond the standard model in events with at least three leptons is presented. The data sample, corresponding to an integrated luminosity of 19.5 fb-1 of proton-proton collisions with center-of-mass energy s=8 TeV, was collected by the CMS experiment at the LHC during 2012. The data are divided into exclusive categories based on the number of leptons and their flavor, the presence or absence of an opposite-sign, same-flavor lepton pair (OSSF), the invariant mass of the OSSF pair, the presence or absence of a tagged bottom-quark jet, the number of identified hadronically decaying τ leptons, and the magnitude of the missing transverse energy and of the scalar sum of jet transverse momenta. The numbers of observed events are found to be consistent with the expected numbers from standard model processes, and limits are placed on new-physics scenarios that yield multilepton final states. In particular, scenarios that predict Higgs boson production in the context of supersymmetric decay chains are examined. We also place a 95% confidence level upper limit of 1.3% on the branching fraction for the decay of a top quark to a charm quark and a Higgs boson (t→cH), which translates to a bound on the left- and right-handed top-charm flavor-violating Higgs Yukawa couplings, λtcH and λctH, respectively, of |λtcH|2+|λctH|2<0.21.

2014

Chargement

Afficher plus

Search for the production of an excited bottom quark decaying to $tW$ in proton-proton collisions at $ \sqrt{s}=8 $ TeV

A search is presented for a singly produced excited bottom quark (b

^{*}

) decaying to a top quark and a W boson in the all-hadronic, lepton+jets, and dilepton final states in proton-proton collisions at

\sqrt{s}=8

TeV recorded by the CMS experiment at the CERN LHC. Data corresponding to an integrated luminosity of 19.7 fb

^{−1}

are used. No significant excess of events is observed with respect to standard model expectations. We set limits at 95% confidence on the product of the b

^{*}

quark production cross section and its branching fraction to tW. The cross section limits are interpreted for scenarios including left-handed, right-handed, and vector-like couplings of the b

^{*}

quark and are presented in the two-dimensional coupling plane based on the production and decay coupling constants. The masses of the left-handed, right-handed, and vector-like b

^{*}

quark states are excluded at 95% confidence below 1390, 1430, and 1530 GeV, respectively, for benchmark couplings. This analysis gives the most stringent limits on the mass of the b

^{∗}

quark to date.

2016

Search for neutral color-octet weak-triplet scalar particles in proton-proton collisions at $ \sqrt{s}=8 $ TeV

A search for pair production of neutral color-octet weak-triplet scalar particles (Θ

^{0}

) is performed in processes where one Θ

^{0}

^{−1}

of proton-proton collisions at

\sqrt{s}=8

^{0}

mass. The 95% confidence level lower bounds on the Θ

^{0}

mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model.

2015