Search for heavy Majorana neutrinos in same-sign dilepton channels in proton-proton collisions at √s =13 TeV

Abstract

A search is performed for a heavy Majorana neutrino (N), produced in leptonic decay of a W boson propagator and decaying into a W boson and a lepton, with the CMS detector at the LHC. The signature used in this search consists of two same-sign leptons, in any flavor combination of electrons and muons, and at least one jet. The data were collected during 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb?1. The results are found to be consistent with the expected standard model background. Upper limits are set in the mass range between 20 and 1600 GeV in the context of a Type-I seesaw mechanism, on |VeN|2, |V?N|2, and |VeNV?N *|2/(|VeN|2 + |V?N|2), where V?N is the matrix element describing the mixing of N with the standard model neutrino of flavor ? = e, ?. For N masses between 20 and 1600 GeV, the upper limits on |V?N|2 range between 2.3 × 10?5 and unity. These are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV.[Figure not available: see fulltext.] © 2019, The Author(s). ; Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP Institut National de Physique Nucléaire et de Physique des Particules, IN2P3 Fonds Wetenschappelijk Onderzoek, FWO Eesti Teadusagentuur, ETAg: IUT23-6, IUT23-4 Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, FAPERJ Austrian Science Fund, FWF Research Promotion Foundation, ???? Hrvatska Zaklada za Znanost, HRZZ Centre National de la Recherche Scientifique, CNRS Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) CERN Ministerio de Ciencia y Tecnología, MICYT Academy of Finland Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES Chinese Academy of Sciences, CAS Bundesministerium für Wissenschaft und Forschung, BMWF Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA European Regional Development Fund, FEDER Utbildningsdepartementet National Natural Science Foundation of China, NSFC Joint Institute for Nuclear Research, JINR Foundation for the Advancement of Theoretical Physics and Mathematics Russian Foundation for Basic Research, ???? National Academy of Sciences of Ukraine, NASU Istituto Nazionale di Fisica Nucleare, INFN Consejo Nacional de Ciencia y Tecnología, CONACYT Universiti Malaya, UM Eidgenössische Technische Hochschule Zürich, ETH Lietuvos Moksl? Akademija Deutsche Forschungsgemeinschaft, DFG Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF Science and Technology Facilities Council, STFC Benemérita Universidad Autónoma de Puebla, BUAP Secretaría de Estado de Investigación, Desarrollo e Innovación, SEIDI Eidgenössischen Departement für Wirtschaft, Bildung und Forschung, WBF National Science Foundation, NSF General Secretariat for Research and Technology, GSRT Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja, MPNTR European Regional Development Fund, FEDER Russian Academy of Sciences, ??? Institute for the Promotion of Teaching Science and Technology, IPST Ministerio de Ciencia y Tecnología, MICYT Federal Agency of Atomic Energy of the Russian Federation Thailand Center of Excellence in Physics Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAK Ministry of Business, Innovation and Employment, MBIE Kementerian Pendidikan Malaysia, KPM Secretaría de Educación Pública, SEP Ministry of Science,Technology and Research, MoSTR School of Energy Resources, University of Wyoming, SER Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV Fundo Regional para a Ciência e Tecnologia, FRCT Ministry of Science, ICT and Future Planning, MSIP U.S. Department of Energy, USDOE Physicians' Services Incorporated Foundation, PSI Türkiye Atom Enerjisi Kurumu, TAEK Ministry of Education and Science of the Russian Federation, Minobrnauka Pakistan Atomic Energy Commission, PAEC European Regional Development Fund, FEDER Bangladesh Council of Scientific and Industrial Research, BCSIR Horizon 2020: 675440 Fundacja na rzecz Nauki Polskiej, FNP Alfred P. Sloan Foundation Belgian Federal Science Policy Office, BELSPO Agentschap voor Innovatie door Wetenschap en Technologie, IWT Alexander von Humboldt-Stiftung Ministerstvo Školství, Mláde?e a T?lov?chovy, MŠMT European Commission, EC A.G. Leventis Foundation Ministerstvo Školství, Mláde?e a T?lov?chovy, MŠMT 30820817 Fonds Wetenschappelijk Onderzoek, FWO European Research Council, ERC Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture, FRIA Magyar Tudományos Akadémia, MTA Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA: 125105, 124850, 123842, 123959, 124845 Welch Foundation: C-1845 Qatar National Research Fund, QNRF Chulalongkorn University, CU Weston Havens Foundation ; Open Access, Copyright CERN, for the benefit of the CMS Collaboration. Article funded by SCOAP3. ; We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: the Austrian Federal Ministry of Science, Research and Economy and the Austrian Science Fund; the Belgian Fonds de la Recherche Scientifique, and Fonds voor Wetenschappelijk Onderzoek; the Brazilian Funding Agencies (CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP); the Bulgarian Ministry of Education and Science; CERN; the Chinese Academy of Sciences, Ministry of Science and Technology, and National Natural Science Foundation of China; the Colombian Funding Agency (COLCIENCIAS); the Croatian Ministry of Science, Education and Sport, and the Croatian Science Foundation; the Research Promotion Foundation, Cyprus; the Secretariat for Higher Education, Science, Technology and Innovation, Ecuador; the Ministry of Education and Research, Estonian Research Council via IUT23-4 and IUT23-6 and European Regional Development Fund, Estonia; the Academy of Finland, Finnish Ministry of Education and Culture, and Helsinki Institute of Physics; the Institut National de Physique Nucléaire et de Physique des Particules / CNRS, and Commissariat à l'Énergie Atomique et aux Énergies Alternatives / CEA, France; the Bundesministerium für ; Bildung und Forschung, Deutsche Forschungsgemeinschaft, and Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany; the General Secretariat for Research and Technology, Greece; the National Research, Development and Innovation Fund, Hungary; the Department of Atomic Energy and the Department of Science and Technology, India; the Institute for Studies in Theoretical Physics and Mathematics, Iran; the Science Foundation, Ireland; the Istituto Nazionale di Fisica Nucleare, Italy; the Ministry of Science, ICT and Future Planning, and National Research Foundation (NRF), Republic of Korea; the Lithuanian Academy of Sciences; the Ministry of Education, and University of Malaya (Malaysia); the Ministry of Science of Montenegro; the Mexican Funding Agencies (BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI); the Ministry of Business, Innovation and Employment, New Zealand; the Pakistan Atomic Energy Commission; the Ministry of Science and Higher Education and the National Science Center, Poland; the Fundac¸ão para a Ciência e a Tecnologia, Portugal; JINR, Dubna; the Ministry of Education and Science of the Russian Federation, the Federal Agency of Atomic Energy of the Russian Federation, Russian Academy of Sciences, the Russian Foundation for Basic Research, and the National Research Center "Kurchatov Institute"; the Ministry of Education, Science and Technological Development of Serbia; the Secretaría de Estado de Investigación, Desarrollo e Innovación, Programa Consolider-Ingenio 2010, Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016, Plan de Ciencia, Tecnología e Innovación 2013-2017 del Principado de Asturias, and Fondo Europeo de Desarrollo Regional, Spain; the Ministry of Science, Technology and Research, Sri Lanka; the Swiss Funding Agencies (ETH Board, ETH Zurich, PSI, SNF, UniZH, Canton Zurich, and SER); the Ministry of Science and Technology, Taipei; the Thailand Center of Excellence in Physics, the Institute for the Promotion of Teaching Science and Technology of Thailand, Special Task Force for Activating Research and the National Science and Technology Development Agency of Thailand; the Scientific and Technical Research Council of Turkey, and Turkish Atomic Energy Authority; the National Academy of Sciences of Ukraine, and State Fund for Fundamental Researches, Ukraine; the Science and Technology Facilities Council, U.K.; the U.S. Department of Energy, and the U.S. National Science Foundation. ; Individuals have received support from the Marie-Curie program and the European Research Council and Horizon 2020 Grant, contract No. 675440 (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the "Excellence of Science — EOS" — be.h project n. 30820817; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Lendület ("Momentum") Program and the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program ÚNKP, the NKFIA research grants 123842, 123959, 124845, 124850 and 125105 (Hungary); the Council of Scientific and Industrial Research, India; the HOMING PLUS program of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobility Plus program of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts ; Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; the National Priorities Research Program by Qatar National Research Fund; the Programa de Excelencia María de Maeztu, and the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programs cofinanced by EU-ESF, and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University, and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Welch Foundation, contract C-1845; and the Weston Havens Foundation (U.S.A.).