https://doi.org/10.1140/epjc/s10052-018-5607-5
Regular Article - Experimental Physics
Search for standard model production of four top quarks with same-sign and multilepton final states in proton–proton collisions at 
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Yerevan Physics Institute, Yerevan, Armenia
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Institut für Hochenergiephysik, Vienna, Austria
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Institute for Nuclear Problems, Minsk, Belarus
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Universiteit Antwerpen, Antwerp, Belgium
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Vrije Universiteit Brussel, Brussels, Belgium
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Université Libre de Bruxelles, Brussels, Belgium
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Ghent University, Ghent, Belgium
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Université Catholique de Louvain, Louvain-la-Neuve, Belgium
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Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil
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Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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Universidade Estadual Paulista, Universidade Federal do ABC, São Paulo, Brazil
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Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria
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University of Sofia, Sofia, Bulgaria
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Beihang University, Beijing, China
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Institute of High Energy Physics, Beijing, China
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State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
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Tsinghua University, Beijing, China
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Universidad de Los Andes, Bogotá, Colombia
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Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia
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Faculty of Science, University of Split, Split, Croatia
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Institute Rudjer Boskovic, Zagreb, Croatia
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University of Cyprus, Nicosia, Cyprus
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Charles University, Prague, Czech Republic
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Universidad San Francisco de Quito, Quito, Ecuador
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Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt
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National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
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Department of Physics, University of Helsinki, Helsinki, Finland
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Helsinki Institute of Physics, Helsinki, Finland
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Lappeenranta University of Technology, Lappeenranta, Finland
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IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France
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Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, Université Paris-Saclay, Palaiseau, France
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Université de Strasbourg, CNRS, IPHC UMR 7178, 67000, Strasbourg, France
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Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France
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Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Villeurbanne, France
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Georgian Technical University, Tbilisi, Georgia
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Tbilisi State University, Tbilisi, Georgia
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RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany
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RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany
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RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany
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Deutsches Elektronen-Synchrotron, Hamburg, Germany
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University of Hamburg, Hamburg, Germany
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Institut für Experimentelle Kernphysik, Karlsruhe, Germany
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Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece
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National and Kapodistrian University of Athens, Athens, Greece
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National Technical University of Athens, Athens, Greece
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University of Ioánnina, Ioannina, Greece
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MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Eötvös Loránd University, Budapest, Hungary
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Wigner Research Centre for Physics, Budapest, Hungary
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Institute of Nuclear Research ATOMKI, Debrecen, Hungary
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Institute of Physics, University of Debrecen, Debrecen, Hungary
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Indian Institute of Science (IISc), Bangalore, India
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National Institute of Science Education and Research, Bhubaneswar, India
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Panjab University, Chandigarh, India
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University of Delhi, Delhi, India
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Saha Institute of Nuclear Physics, HBNI, Kolkata, India
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Indian Institute of Technology Madras, Madras, India
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Bhabha Atomic Research Centre, Mumbai, India
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Tata Institute of Fundamental Research-A, Mumbai, India
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Tata Institute of Fundamental Research-B, Mumbai, India
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Indian Institute of Science Education and Research (IISER), Pune, India
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Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
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University College Dublin, Dublin, Ireland
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INFN Sezione di Bari, Università di Bari, Politecnico di Bari, Bari, Italy
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INFN Sezione di Bologna, Università di Bologna, Bologna, Italy
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INFN Sezione di Catania, Università di Catania, Catania, Italy
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INFN Sezione di Firenze, Università di Firenze, Florence, Italy
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INFN Laboratori Nazionali di Frascati, Frascati, Italy
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INFN Sezione di Genova, Università di Genova, Genoa, Italy
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INFN Sezione di Milano-Bicocca, Università di Milano-Bicocca, Milan, Italy
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INFN Sezione di Napoli, Università di Napoli ‘Federico II’, Naples, Italy, Università della Basilicata, Potenza, Italy, Università G. Marconi, Rome, Italy
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INFN Sezione di Padova, Università di Padova, Padua, Italy, Università di Trento, Trento, Italy
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INFN Sezione di Pavia, Università di Pavia, Pavia, Italy
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INFN Sezione di Perugia, Università di Perugia, Perugia, Italy
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INFN Sezione di Pisa, Università di Pisa, Scuola Normale Superiore di Pisa, Pisa, Italy
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INFN Sezione di Roma, Università di Roma, Rome, Italy
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INFN Sezione di Torino, Università di Torino, Turin, Italy, Università del Piemonte Orientale, Novara, Italy
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INFN Sezione di Trieste, Università di Trieste, Trieste, Italy
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Kyungpook National University, Daegu, Korea
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Institute for Universe and Elementary Particles, Chonnam National University, Kwangju, Korea
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Hanyang University, Seoul, Korea
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Korea University, Seoul, Korea
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Seoul National University, Seoul, Korea
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University of Seoul, Seoul, Korea
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Sungkyunkwan University, Suwon, Korea
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Vilnius University, Vilnius, Lithuania
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National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia
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Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico
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Universidad Iberoamericana, Mexico City, Mexico
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Benemerita Universidad Autonoma de Puebla, Puebla, Mexico
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Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
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University of Auckland, Auckland, New Zealand
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University of Canterbury, Christchurch, New Zealand
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National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan
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National Centre for Nuclear Research, Swierk, Poland
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Faculty of Physics, Institute of Experimental Physics, University of Warsaw, Warsaw, Poland
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Laboratório de Instrumentação e Física Experimental de Partículas, Lisbon, Portugal
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Joint Institute for Nuclear Research, Dubna, Russia
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Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia
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Institute for Nuclear Research, Moscow, Russia
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Institute for Theoretical and Experimental Physics, Moscow, Russia
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Moscow Institute of Physics and Technology, Moscow, Russia
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National Research Nuclear University ‘Moscow Engineering Physics Institute’ (MEPhI), Moscow, Russia
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P.N. Lebedev Physical Institute, Moscow, Russia
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Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia
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Novosibirsk State University (NSU), Novosibirsk, Russia
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State Research Center of Russian Federation, Institute for High Energy Physics of NRC “Kurchatov Institute”, Protvino, Russia
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Faculty of Physics and Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
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Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
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Universidad Autónoma de Madrid, Madrid, Spain
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Universidad de Oviedo, Oviedo, Spain
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Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain
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CERN, European Organization for Nuclear Research, Geneva, Switzerland
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Paul Scherrer Institut, Villigen, Switzerland
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Institute for Particle Physics and Astrophysics (IPA), ETH Zurich, Zurich, Switzerland
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Universität Zürich, Zurich, Switzerland
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National Central University, Chung-Li, Taiwan
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National Taiwan University (NTU), Taipei, Taiwan
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Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
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Physics Department, Science and Art Faculty, Çukurova University, Adana, Turkey
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Physics Department, Middle East Technical University, Ankara, Turkey
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Bogazici University, Istanbul, Turkey
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Istanbul Technical University, Istanbul, Turkey
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Institute for Scintillation Materials of National Academy of Science of Ukraine, Kharkov, Ukraine
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National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine
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University of Bristol, Bristol, UK
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Rutherford Appleton Laboratory, Didcot, UK
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Imperial College, London, UK
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Brunel University, Uxbridge, UK
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Baylor University, Waco, USA
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Catholic University of America, Washington, DC, USA
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The University of Alabama, Tuscaloosa, USA
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Boston University, Boston, USA
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Brown University, Providence, USA
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University of California, Davis, Davis, USA
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University of California, Los Angeles, USA
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University of California, Riverside, Riverside, USA
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University of California, San Diego, La Jolla, USA
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Santa Barbara-Department of Physics, University of California, Santa Barbara, USA
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California Institute of Technology, Pasadena, USA
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Carnegie Mellon University, Pittsburgh, USA
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University of Colorado Boulder, Boulder, USA
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Cornell University, Ithaca, USA
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Fermi National Accelerator Laboratory, Batavia, USA
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University of Florida, Gainesville, USA
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Florida International University, Miami, USA
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Florida State University, Tallahassee, USA
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Florida Institute of Technology, Melbourne, USA
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University of Illinois at Chicago (UIC), Chicago, USA
149
The University of Iowa, Iowa City, USA
150
Johns Hopkins University, Baltimore, USA
151
The University of Kansas, Lawrence, USA
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Kansas State University, Manhattan, USA
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Lawrence Livermore National Laboratory, Livermore, USA
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University of Maryland, College Park, USA
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Massachusetts Institute of Technology, Cambridge, USA
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University of Minnesota, Minneapolis, USA
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University of Mississippi, Oxford, USA
158
University of Nebraska-Lincoln, Lincoln, USA
159
State University of New York at Buffalo, Buffalo, USA
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Northeastern University, Boston, USA
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Northwestern University, Evanston, USA
162
University of Notre Dame, Notre Dame, USA
163
The Ohio State University, Columbus, USA
164
Princeton University, Princeton, USA
165
University of Puerto Rico, Mayagüez, USA
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Purdue University, West Lafayette, USA
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Purdue University Northwest, Hammond, USA
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Rice University, Houston, USA
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University of Rochester, Rochester, USA
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The Rockefeller University, New York, USA
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Rutgers, The State University of New Jersey, Piscataway, USA
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University of Tennessee, Knoxville, USA
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Texas A&M University, College Station, USA
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Texas Tech University, Lubbock, USA
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Vanderbilt University, Nashville, USA
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University of Virginia, Charlottesville, USA
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Wayne State University, Detroit, USA
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University of Wisconsin-Madison, Madison, WI, USA
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CERN, 1211, Geneva 23, Switzerland
* e-mail: cms-publication-committee-chair@cern.ch
Received:
29
October
2017
Accepted:
31
January
2018
Published online:
19
February
2018
A search for standard model production of four top quarks (
) is reported using events containing at least three leptons (
) or a same-sign lepton pair. The events are produced in proton–proton collisions at a center-of-mass energy of 13
at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9
. 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 cross section is measured to be 
, 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.
© CERN for the benefit of the CMS collaboration, 2018
