ATLAS Collaboration (Including: Farrington, Sinead, Jeske, C., Jones, G. (Graham), Martin, T. A. and Pianori, E.). (2014) Study of heavy-flavor quarks produced in association with top-quark pairs at s =7TeV using the ATLAS detector. Physical Review D - Particles, Fields, Gravitation and Cosmology , Volume 89 (Number 7). Article number 072012. doi:10.1103/PhysRevD.89.072012 ISSN 1550-7998.

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Abstract

Using a sample of dilepton top-quark pair (tt̄) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of tt̄+b+X and tt̄+c+X, collectively referred to as tt̄+HF. The data set used corresponds to an integrated luminosity of 4.7fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the tt̄ sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the tt̄ decays and the third to additional HF production. The dominant background to tt̄+HF in this sample is tt̄+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79±14(stat)±22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero tt̄+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for tt̄+HF production to the cross section for tt̄ production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2±1.1(stat)±1.8(syst)]% for jets with pT>25GeV and |η|<2.5, in agreement with the expectations from Monte Carlo generators.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Quarks, Particles (Nuclear physics) -- Flavor
Journal or Publication Title:	Physical Review D - Particles, Fields, Gravitation and Cosmology
Publisher:	American Physical Society
ISSN:	1550-7998
Official Date:	21 April 2014
Dates:	Date Event 21 April 2014 Published 23 April 2014 Submitted
Volume:	Volume 89
Number:	Number 7
Number of Pages:	23
Article Number:	Article number 072012
DOI:	10.1103/PhysRevD.89.072012
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access (Creative Commons)
Date of first compliant deposit:	27 December 2015
Date of first compliant Open Access:	27 December 2015
Funder:	European Organization for Nuclear Research (CERN), Agencia Nacional de Promoción Científica y Tecnológica (Argentina), Yerevan Physics Institute (Armenia), Australian Research Council (ARC), Austria. Bundesministerium für Wissenschaft und Forschung [Federal Ministry of Education, Science and Culture], Fonds zur Förderung der Wissenschaftlichen Forschung (Austria) (FWF), Azärbaycan Milli Elmlär Akademiyası, Belarus.‏ ‎Gosudarstvennyĭ komitet po nauke i tekhnologii︠a︡m‏, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Natural Sciences and Engineering Research Council of Canada (NSERC), National Research Council Canada (NRCC), Canada Foundation for Innovation (CFI), Chile. Comisión Nacional de Investigación Científica y Tecnológica (CONICYT), Zhongguo ke xue yuan [Chinese Academy of Sciences] (CAS), Guo jia zi ran ke xue ji jin wei yuan hui (China) [National Natural Science Foundation of China] (NSFC), China. Guo jia ke xue ji shu bu [Ministry of Science and Technology], ondo Colombiano de Investigaciones Científicas y Proyectos Especiales Francisco José de Caldas (COLCIENCIAS), VSC CR (Czech Republic), Czech Republic. Ministerstvo školství, mládeže a tělovýchovy [Ministry of Education, Youth, and Sport], Czech Republic.‏ ‎Ministerstvo průmyslu a obchodu‏ [Ministery of Industry and Trade] (MPO), Lundbeck Foundation, Danmarks Grundforskningsfond [Danish National Research Foundation], Statens naturvidenskabelige forskningsråd (Denmark) [Natural Science Research Council], European Particle physics Latin American NETwork (EPLANET), European Research Council (ERC), Institut national de physique nucléaire et de physique des particules (IN2P3), Centre national de la recherche scientifique (France) (CNRS), France. Commissariat à l'énergie atomique (CEA), Sakʻartʻvelos mecʻnierebatʻa erovnuli akademia [Georgian National Academy of Sciences] (GNAS), Germany. Bundesministerium für Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Max-Planck-Gesellschaft zur Förderung der Wissenschaften [Max Planck Society for the Advancement of Science], Alexander von Humboldt-Stiftung (AvHS), Greece. General Secretariat of Research and Technology, Israel Science Foundation (ISF), Minerva Stiftung, German-Israeli Foundation for Scientific Research and Development, Israeli Centers of Research Excellence (I-CORE), Benoziyo Center (Israel), Istituto nazionale di fisica nucleare (INFN), Japan. Monbu Kagakushō [Japan. Ministry of Education, Culture, Sports, Science and Technology] (MK), Nihon Gakujutsu Shinkōkai [Japan Society for the Promotion of Science] (NGS), Centre national pour la recherche scientifique et technique (Morocco), Stichting voor Fundamenteel Onderzoek der Materie (FOM) [Foundation for Fundamental Research on Matter], Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Netherlands Organisation for Scientific Research] (NWO), Norges forskningsråd [Norwegian Research Council], BRF (Norway), Poland. Ministerstwo Nauki i Szkolnictwa Wyższego [Ministry of Science and Higher Education] (MNiSW), Narodowe Centrum Nauki (NCN), Portugal.‏ Ministério da Ciência, da Inovação e do Ensino Superior, Fundação para a Ciência e a Tecnologia (FCT), Romania.‏ Ministerul Educației Naționale‏ (MNE), Institutul de Fizică Atomică (IFA), Russia (Federation). Ministerstvo obrazovanii︠a︡ [Ministry of Education], Federalʹnoe agentstvo po atomnoĭ ėnergii (Russia), Serbia. Joint Institute for Nuclear Research (JINR), Serbia. Ministarstvo prosvete i sporta‏ [Ministry of Education] (MSTD), Slovenia. Ministerstvo Spravodlivosti Slovenskej Republiky, Slovenian Research Agency, Slovenia.‏ Ministrstvo za šolstvo, znanost in šport‏, South Africa. Department of Science and Technology, National Research Foundation (South Africa) (NRF), Spain. Ministerio de Economía y Competitividad [Ministry of Economy and Competitiveness] (MINECO), Sweden. Vetenskapsrådet [Research Council], Knut och Alice Wallenbergs Stiftelse (Sweden), Switzerland. Staatssekretariat für Ausbildung und Forschung (SER), Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung [Swiss National Science Foundation] (SNSF), Bern (Switzerland : Canton), Türkiye Atom Enerjisi Kurumu (TAEK), Geneva (Switzerland : Canton), China. Guo jia ke xue ji shu bu [Ministry of Science and Technology], National Strategic Research Framework (Greece), Science and Technology Facilities Council (Great Britain) (STFC), Royal Society (Great Britain), Leverhulme Trust (LT), United States. Department of Energy, National Science Foundation (U.S.) (NSF)

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