Search for heavy Majorana neutrinos in μ±μ± + jets events in proton–proton collisions at √s = 8 TeV

Creators: Khachatryan, V.; Apresyan, A.; Bornheim, A.; Bunn, J.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Pierini, M.; Spiropulu, M.; Vlimant, J. R.; Wilkinson, R.; Xie, S.; Zhu, R. Y.; Dubinin, M.; Chen, Y.; CMS Collaboration

Abstract

A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two muons of the same charge and two jets (μ±μ±jj). The data correspond to an integrated luminosity of 19.7fb^(−1) of proton–proton collisions at a center-of-mass energy of 8TeV, collected with the CMS detector at the CERN LHC. No excess of events is observed beyond the expected standard model background and upper limits are set on |V_(μN)|^2 as a function of Majorana neutrino mass m_N for masses in the range of 40–500GeV, where V_(μN) is the mixing element of the heavy neutrino with the standard model muon neutrino. The limits obtained are |V_(μN)|^2<0.00470 for m_N=90GeV, |V_(μN)|^2<0.0123 for m_N=200GeV, and |V_(μN)|^2<0.583 for m_N=500GeV. These results extend considerably the regions excluded by previous direct searches.

Additional Information

© 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3. Received 22 January 2015; Received in revised form 15 May 2015; Accepted 28 June 2015; Available online 2 July 2015. Editor: M. Doser. We would like to thank Juan Antonio Aguliar-Saavedra, Francisco del Aguila, and Tao Han for assistance with Monte Carlo generators and calculations of the heavy neutrino branching fractions, as well as for advice on the theoretical interpretations of our results. 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: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); MoER, ERC IUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie program and the European Research Council and EPLANET (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 Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Council of Science and Industrial Research, India; the HOMING PLUS program of Foundation for Polish Science, co-financed from European Union, Regional Development Fund; the Compagnia di San Paolo (Torino); the Consorzio per la Fisica (Trieste); MIUR project 20108T4XTM (Italy); the Thalis and Aristeia programs co-financed by EU-ESF and the Greek NSRF; and the National Priorities Research Program by Qatar National Research Fund.

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