https://doi.org/10.1140/epjc/s10052-018-5995-6
Regular Article - Experimental Physics
Search for heavy particles decaying into top-quark pairs using lepton-plus-jets events in proton–proton collisions at 
with the ATLAS detector
1
Department of Physics, University of Adelaide, Adelaide, Australia
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Physics Department, SUNY Albany, Albany, NY, USA
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Department of Physics, University of Alberta, Edmonton, AB, Canada
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Department of Physics, Ankara University, Ankara, Turkey
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Istanbul Aydin University, Istanbul, Turkey
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Division of Physics, TOBB University of Economics and Technology, Ankara, Turkey
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LAPP, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, Annecy, France
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High Energy Physics Division, Argonne National Laboratory, Argonne, IL, USA
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Department of Physics, University of Arizona, Tucson, AZ, USA
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Department of Physics, The University of Texas at Arlington, Arlington, TX, USA
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Physics Department, National and Kapodistrian University of Athens, Athens, Greece
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Physics Department, National Technical University of Athens, Zografou, Greece
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Department of Physics, The University of Texas at Austin, Austin, TX, USA
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Faculty of Engineering and Natural Sciences, Bahcesehir University, Istanbul, Turkey
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Faculty of Engineering and Natural Sciences, Istanbul Bilgi University, Istanbul, Turkey
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Department of Physics, Bogazici University, Istanbul, Turkey
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Department of Physics Engineering, Gaziantep University, Gaziantep, Turkey
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Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan
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Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Barcelona, Spain
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Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
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Department of Physics, Nanjing University, Jiangsu, China
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Physics Department, Tsinghua University, Beijing, China
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University of Chinese Academy of Science (UCAS), Beijing, China
24
Institute of Physics, University of Belgrade, Belgrade, Serbia
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Department for Physics and Technology, University of Bergen, Bergen, Norway
26
Physics Division, Lawrence Berkeley National Laboratory and University of California, Berkeley, CA, USA
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Department of Physics, Humboldt University, Berlin, Germany
28
Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics, University of Bern, Bern, Switzerland
29
School of Physics and Astronomy, University of Birmingham, Birmingham, UK
30
Centro de Investigaciones, Universidad Antonio Narino, Bogotá, Colombia
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Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy
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INFN Sezione di Bologna, Bologna, Italy
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Physikalisches Institut, University of Bonn, Bonn, Germany
34
Department of Physics, Boston University, Boston, MA, USA
35
Department of Physics, Brandeis University, Waltham, MA, USA
36
Transilvania University of Brasov, Brasov, Romania
37
Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
38
Department of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, Romania
39
Physics Department, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania
40
University Politehnica Bucharest, Bucharest, Romania
41
West University in Timisoara, Timisoara, Romania
42
Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovak Republic
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Department of Subnuclear Physics, Institute of Experimental Physics of the Slovak Academy of Sciences, Kosice, Slovak Republic
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Physics Department, Brookhaven National Laboratory, Upton, NY, USA
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Departamento de Física, Universidad de Buenos Aires, Buenos Aires, Argentina
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Cavendish Laboratory, University of Cambridge, Cambridge, UK
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Department of Physics, University of Cape Town, Cape Town, South Africa
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Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg, South Africa
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School of Physics, University of the Witwatersrand, Johannesburg, South Africa
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Department of Physics, Carleton University, Ottawa, ON, Canada
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Faculté des Sciences Ain Chock, Réseau Universitaire de Physique des Hautes Energies-Université Hassan II, Casablanca, Morocco
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Centre National de l’Energie des Sciences Techniques Nucleaires, Rabat, Morocco
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Faculté des Sciences Semlalia, Université Cadi Ayyad, LPHEA-Marrakech, Marrakech, Morocco
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Faculté des Sciences, Université Mohamed Premier and LPTPM, Oujda, Morocco
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Faculté des sciences, Université Mohammed V, Rabat, Morocco
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CERN, Geneva, Switzerland
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Enrico Fermi Institute, University of Chicago, Chicago, IL, USA
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LPC, Université Clermont Auvergne, CNRS/IN2P3, Clermont-Ferrand, France
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Nevis Laboratory, Columbia University, Irvington, NY, USA
60
Niels Bohr Institute, University of Copenhagen, Kobenhavn, Denmark
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Dipartimento di Fisica, Università della Calabria, Rende, Italy
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INFN Gruppo Collegato di Cosenza, Laboratori Nazionali di Frascati, Frascati, Italy
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Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland
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Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland
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Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland
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Physics Department, Southern Methodist University, Dallas, TX, USA
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Physics Department, University of Texas at Dallas, Richardson, TX, USA
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Department of Physics, Stockholm University, Stockholm, Sweden
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The Oskar Klein Centre, Stockholm, Sweden
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DESY, Hamburg and Zeuthen, Germany
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Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, Dortmund, Germany
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Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany
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Department of Physics, Duke University, Durham, NC, USA
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SUPA-School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules (IN2P3), Villeurbanne, France
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INFN e Laboratori Nazionali di Frascati, Frascati, Italy
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Fakultät für Mathematik und Physik, Albert-Ludwigs-Universität, Freiburg, Germany
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II Physikalisches Institut, Georg-August-Universität, Göttingen, Germany
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Departement de Physique Nucléaire et Corpusculaire, Université de Genève, Geneva, Switzerland
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Dipartimento di Fisica, Università di Genova, Genoa, Italy
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INFN Sezione di Genova, Genoa, Italy
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II. Physikalisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany
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SUPA-School of Physics and Astronomy, University of Glasgow, Glasgow, UK
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LPSC, Université Grenoble Alpes, CNRS/IN2P3, Grenoble INP, Grenoble, France
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Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, MA, USA
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Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Anhui, China
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School of Physics, Shandong University, Shandong, China
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School of Physics and Astronomy, Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education, Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University, Shanghai, China
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Tsung-Dao Lee Institute, Shanghai, China
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Kirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
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Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
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Faculty of Applied Information Science, Hiroshima Institute of Technology, Hiroshima, Japan
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Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
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Department of Physics, The University of Hong Kong, Hong Kong, China
95
Department of Physics, Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
96
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
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Department of Physics, Indiana University, Bloomington, IN, USA
98
INFN Gruppo Collegato di Udine, Sezione di Trieste, Udine, Italy
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ICTP, Trieste, Italy
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Dipartimento di Chimica, Fisica e Ambiente, Università di Udine, Udine, Italy
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INFN Sezione di Lecce, Lecce, Italy
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Dipartimento di Matematica e Fisica, Università del Salento, Lecce, Italy
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INFN Sezione di Milano, Milan, Italy
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Dipartimento di Fisica, Università di Milano, Milan, Italy
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INFN Sezione di Napoli, Naples, Italy
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Dipartimento di Fisica, Università di Napoli, Naples, Italy
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INFN Sezione di Pavia, Pavia, Italy
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Dipartimento di Fisica, Università di Pavia, Pavia, Italy
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INFN Sezione di Pisa, Pisa, Italy
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Dipartimento di Fisica E. Fermi, Università di Pisa, Pisa, Italy
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INFN Sezione di Roma, Rome, Italy
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Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
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INFN Sezione di Roma Tor Vergata, Rome, Italy
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Dipartimento di Fisica, Università di Roma Tor Vergata, Rome, Italy
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INFN Sezione di Roma Tre, Rome, Italy
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Dipartimento di Matematica e Fisica, Università Roma Tre, Rome, Italy
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INFN-TIFPA, Trento, Italy
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University of Trento, Trento, Italy
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Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität, Innsbruck, Austria
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University of Iowa, Iowa City, IA, USA
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Department of Physics and Astronomy, Iowa State University, Ames, IA, USA
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Joint Institute for Nuclear Research, JINR Dubna, Dubna, Russia
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KEK, High Energy Accelerator Research Organization, Tsukuba, Japan
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Graduate School of Science, Kobe University, Kobe, Japan
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Faculty of Science, Kyoto University, Kyoto, Japan
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Kyoto University of Education, Kyoto, Japan
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Research Center for Advanced Particle Physics and Department of Physics, Kyushu University, Fukuoka, Japan
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Instituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, Argentina
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Physics Department, Lancaster University, Lancaster, UK
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Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK
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Department of Experimental Particle Physics, Jožef Stefan Institute and Department of Physics, University of Ljubljana, Ljubljana, Slovenia
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School of Physics and Astronomy, Queen Mary University of London, London, UK
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Department of Physics, Royal Holloway University of London, Surrey, UK
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Department of Physics and Astronomy, University College London, London, UK
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Louisiana Tech University, Ruston, LA, USA
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Laboratoire de Physique Nucléaire et de Hautes Energies, UPMC and Université Paris-Diderot and CNRS/IN2P3, Paris, France
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Fysiska institutionen, Lunds universitet, Lund, Sweden
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Departamento de Fisica Teorica C-15 and CIAFF, Universidad Autonoma de Madrid, Madrid, Spain
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Institut für Physik, Universität Mainz, Mainz, Germany
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School of Physics and Astronomy, University of Manchester, Manchester, UK
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CPPM, Aix-Marseille Université and CNRS/IN2P3, Marseille, France
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Department of Physics, University of Massachusetts, Amherst, MA, USA
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Department of Physics, McGill University, Montreal, QC, Canada
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School of Physics, University of Melbourne, Melbourne, VIC, Australia
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Department of Physics, The University of Michigan, Ann Arbor, MI, USA
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Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA
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B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Republic of Belarus
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Research Institute for Nuclear Problems of Byelorussian State University, Minsk, Republic of Belarus
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Group of Particle Physics, University of Montreal, Montreal, QC, Canada
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P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia
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Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia
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National Research Nuclear University MEPhI, Moscow, Russia
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D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
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Fakultät für Physik, Ludwig-Maximilians-Universität München, Munich, Germany
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Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Munich, Germany
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Nagasaki Institute of Applied Science, Nagasaki, Japan
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Graduate School of Science and Kobayashi-Maskawa Institute, Nagoya University, Nagoya, Japan
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Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
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Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, The Netherlands
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Nikhef National Institute for Subatomic Physics, University of Amsterdam, Amsterdam, The Netherlands
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Department of Physics, Northern Illinois University, DeKalb, IL, USA
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Budker Institute of Nuclear Physics, SB RAS, Novosibirsk, Russia
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Novosibirsk State University, Novosibirsk, Russia
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Department of Physics, New York University, New York, NY, USA
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Ohio State University, Columbus, OH, USA
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Faculty of Science, Okayama University, Okayama, Japan
167
Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, USA
168
Department of Physics, Oklahoma State University, Stillwater, OK, USA
169
Palacký University, RCPTM, Olomouc, Czech Republic
170
Center for High Energy Physics, University of Oregon, Eugene, OR, USA
171
LAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France
172
Graduate School of Science, Osaka University, Osaka, Japan
173
Department of Physics, University of Oslo, Oslo, Norway
174
Department of Physics, Oxford University, Oxford, UK
175
Department of Physics, University of Pennsylvania, Philadelphia, PA, USA
176
Konstantinov Nuclear Physics Institute of National Research Centre “Kurchatov Institute”, PNPI, St. Petersburg, Russia
177
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, USA
178
Laboratório de Instrumentação e Física Experimental de Partículas-LIP, Lisbon, Portugal
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Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
180
Department of Physics, University of Coimbra, Coimbra, Portugal
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Centro de Física Nuclear da Universidade de Lisboa, Lisbon, Portugal
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Departamento de Fisica, Universidade do Minho, Braga, Portugal
183
Departamento de Fisica Teorica y del Cosmos, Universidad de Granada, Granada, Spain
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Dep Fisica and CEFITEC of Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
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Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
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Czech Technical University in Prague, Praha, Czech Republic
187
Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
188
State Research Center Institute for High Energy Physics (Protvino), NRC KI, Protvino, Russia
189
Particle Physics Department, Rutherford Appleton Laboratory, Didcot, UK
190
Universidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro, Brazil
191
Electrical Circuits Department, Federal University of Juiz de Fora (UFJF), Juiz de Fora, Brazil
192
Federal University of Sao Joao del Rei (UFSJ), Sao Joao del Rei, Brazil
193
Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, Brazil
194
Institut de Recherches sur les Lois Fondamentales de l’Univers, DSM/IRFU, CEA Saclay, Gif-sur-Yvette, France
195
Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, CA, USA
196
Departamento de Física, Pontificia Universidad Católica de Chile, Santiago, Chile
197
Departamento de Física, Universidad Técnica Federico Santa María, Valparaiso, Chile
198
Department of Physics, University of Washington, Seattle, WA, USA
199
Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
200
Department of Physics, Shinshu University, Nagano, Japan
201
Department Physik, Universität Siegen, Siegen, Germany
202
Department of Physics, Simon Fraser University, Burnaby, BC, Canada
203
SLAC National Accelerator Laboratory, Stanford, CA, USA
204
Physics Department, Royal Institute of Technology, Stockholm, Sweden
205
Departments of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
206
Department of Physics and Astronomy, University of Sussex, Brighton, UK
207
School of Physics, University of Sydney, Sydney, Australia
208
Institute of Physics, Academia Sinica, Taipei, Taiwan
209
E. Andronikashvili Institute of Physics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia
210
High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia
211
Department of Physics, Technion: Israel Institute of Technology, Haifa, Israel
212
Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
213
Department of Physics, Aristotle University of Thessaloniki, Thessaloníki, Greece
214
International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan
215
Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan
216
Department of Physics, Tokyo Institute of Technology, Tokyo, Japan
217
Tomsk State University, Tomsk, Russia
218
Department of Physics, University of Toronto, Toronto, ON, Canada
219
TRIUMF, Vancouver, BC, Canada
220
Department of Physics and Astronomy, York University, Toronto, ON, Canada
221
Division of Physics and Tomonaga Center for the History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan
222
Department of Physics and Astronomy, Tufts University, Medford, MA, USA
223
Academia Sinica Grid Computing, Institute of Physics, Academia Sinica, Taipei, Taiwan
224
Department of Physics and Astronomy, University of California Irvine, Irvine, CA, USA
225
Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden
226
Department of Physics, University of Illinois, Urbana, IL, USA
227
Instituto de Fisica Corpuscular (IFIC), Centro Mixto Universidad de Valencia-CSIC, Valencia, Spain
228
Department of Physics, University of British Columbia, Vancouver, BC, Canada
229
Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
230
Fakultät für Physik und Astronomie, Julius-Maximilians-Universität, Würzburg, Germany
231
Department of Physics, University of Warwick, Coventry, UK
232
Waseda University, Tokyo, Japan
233
Department of Particle Physics, The Weizmann Institute of Science, Rehovot, Israel
234
Department of Physics, University of Wisconsin, Madison, WI, USA
235
Fakultät für Mathematik und Naturwissenschaften, Fachgruppe Physik, Bergische Universität Wuppertal, Wuppertal, Germany
236
Department of Physics, Yale University, New Haven, CT, USA
237
Yerevan Physics Institute, Yerevan, Armenia
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Received:
1
May
2018
Accepted:
14
June
2018
Published online:
9
July
2018
Abstract
A search for new heavy particles that decay into top-quark pairs is performed using data collected from proton–proton collisions at a centre-of-mass energy of 13 by the ATLAS detector at the Large Hadron Collider. The integrated luminosity of the data sample is 36.1 fb
. Events consistent with top-quark pair production are selected by requiring a single isolated charged lepton, missing transverse momentum and jet activity compatible with a hadronic top-quark decay. Jets identified as likely to contain b-hadrons are required to reduce the background from other Standard Model processes. The invariant mass spectrum of the candidate top-quark pairs is examined for local excesses above the background expectation. No significant deviations from the Standard Model predictions are found. Exclusion limits are set on the production cross-section times branching ratio for hypothetical 
bosons, Kaluza–Kein gluons and Kaluza–Klein gravitons that decay into top-quark pairs.
© CERN for the benefit of the ATLAS collaboration, 2018
