Regular Article - Experimental Physics

The European Physical Journal C

, Volume 52, Issue 4, pp 833-847

First online:

Search for lepton flavour violation in ep collisions at HERA

  • A. AktasAffiliated withDESY
  • , C. AlexaAffiliated withDESYNational Institute for Physics and Nuclear Engineering, Magurele
  • , V. AndreevAffiliated withLebedev Physical Institute
  • , T. AnthonisAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
  • , B. AntunovicAffiliated withMax-Planck-Institut für Physik
  • , S. AplinAffiliated withDESY
  • , A. AsmoneAffiliated withDipartimento di Fisica Università di Roma Tre and INFN Roma 3
  • , A. AstvatsatourovAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
  • , A. BabaevAffiliated withInstitute for Theoretical and Experimental Physics
    • , S. BackovicAffiliated withFaculty of Science, University of Montenegro
    • , A. BaghdasaryanAffiliated withYerevan Physics Institute
    • , P. BaranovAffiliated withLebedev Physical Institute
    • , E. BarreletAffiliated withLPNHE, Universités Paris VI and VII, IN2P3-CNRS
    • , W. BartelAffiliated withDESY
    • , S. BaudrandAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , M. BeckinghamAffiliated withDESY
    • , K. BegzsurenAffiliated withInstitute of Physics and Technology of the Mongolian Academy of Sciences
    • , O. BehnkeAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , O. BehrendtAffiliated withInstitut für Physik, Universität Dortmund
    • , A. BelousovAffiliated withLebedev Physical Institute
    • , N. BergerAffiliated withInstitut für Teilchenphysik, ETH
    • , J.C. BizotAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , M.-O. BoenigAffiliated withInstitut für Physik, Universität Dortmund
    • , V. BoudryAffiliated withLLR, Ecole Polytechnique, IN2P3-CNRS
    • , I. Bozovic-JelisavcicAffiliated withVinca Institute of Nuclear Sciences
    • , J. BracinikAffiliated withMax-Planck-Institut für Physik
    • , G. BrandtAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , M. BrinkmannAffiliated withDESY
    • , V. BrissonAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , D. BrunckoAffiliated withInstitute of Experimental Physics, Slovak Academy of Sciences
    • , F.W. BüsserAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , A. BunyatyanAffiliated withMax-Planck-Institut für KernphysikYerevan Physics Institute
    • , G. BuschhornAffiliated withMax-Planck-Institut für Physik
    • , L. BystritskayaAffiliated withInstitute for Theoretical and Experimental Physics
    • , A.J. CampbellAffiliated withDESY
    • , K.B. Cantun AvilaAffiliated withDepartamento de Fisica Aplicada, CINVESTAV
    • , F. Cassol-BrunnerAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee
    • , K. CernyAffiliated withFaculty of Mathematics and Physics, Charles University
    • , V. CernyAffiliated withInstitute of Experimental Physics, Slovak Academy of SciencesComenius University
    • , V. ChekelianAffiliated withMax-Planck-Institut für Physik
    • , A. CholewaAffiliated withDESY
    • , J.G. ContrerasAffiliated withDepartamento de Fisica Aplicada, CINVESTAV
    • , J.A. CoughlanAffiliated withRutherford Appleton Laboratory, Chilton
    • , G. CozzikaAffiliated withCEA, DSM/DAPNIA, CE-Saclay
    • , J. CvachAffiliated withInstitute of Physics, Academy of Sciences of the Czech Republic
    • , J.B. DaintonAffiliated withDepartment of Physics, University of Liverpool
    • , K. DaumAffiliated withFachbereich C, Universität WuppertalRechenzentrum, Universität Wuppertal
    • , Y. de BoerAffiliated withInstitute for Theoretical and Experimental Physics
    • , B. DelcourtAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , M. Del DeganAffiliated withInstitut für Teilchenphysik, ETH
    • , A. De RoeckAffiliated withDESYCERN
    • , E.A. De WolfAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , C. DiaconuAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee Email author 
    • , V. DodonovAffiliated withMax-Planck-Institut für Kernphysik
    • , A. DubakAffiliated withFaculty of Science, University of MontenegroMax-Planck-Institut für Physik
    • , G. EckerlinAffiliated withDESY
    • , V. EfremenkoAffiliated withInstitute for Theoretical and Experimental Physics
    • , S. EgliAffiliated withPaul Scherrer Institut
    • , R. EichlerAffiliated withPaul Scherrer Institut
    • , F. EiseleAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , A. EliseevAffiliated withLebedev Physical Institute
    • , E. ElsenAffiliated withDESY
    • , S. EssenovAffiliated withInstitute for Theoretical and Experimental Physics
    • , A. FalkewiczAffiliated withInstitute for Nuclear Physics
    • , P.J.W. FaulknerAffiliated withSchool of Physics and Astronomy, University of Birmingham
    • , L. FavartAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , A. FedotovAffiliated withInstitute for Theoretical and Experimental Physics
    • , R. FelstAffiliated withDESY
    • , J. FeltesseAffiliated withCEA, DSM/DAPNIA, CE-SaclayHelmholtz Humboldt Research Award, DESY and University Hamburg
    • , J. FerenceiAffiliated withInstitute of Experimental Physics, Slovak Academy of Sciences
    • , L. FinkeAffiliated withDESY
    • , M. FleischerAffiliated withDESY
    • , A. FomenkoAffiliated withLebedev Physical Institute
    • , G. FrankeAffiliated withDESY
    • , T. FrissonAffiliated withLLR, Ecole Polytechnique, IN2P3-CNRS
    • , E. GabathulerAffiliated withDepartment of Physics, University of Liverpool
    • , E. GaruttiAffiliated withDESY
    • , J. GaylerAffiliated withDESY
    • , S. GhazaryanAffiliated withYerevan Physics Institute
    • , S. GinzburgskayaAffiliated withInstitute for Theoretical and Experimental Physics
    • , A. GlazovAffiliated withDESY
    • , I. GlushkovAffiliated withDESY
    • , L. GoerlichAffiliated withInstitute for Nuclear Physics
    • , M. GoettlichAffiliated withDESY
    • , N. GogitidzeAffiliated withLebedev Physical Institute
    • , S. GorbounovAffiliated withDESY
    • , M. GouzevitchAffiliated withLLR, Ecole Polytechnique, IN2P3-CNRS
    • , C. GrabAffiliated withInstitut für Teilchenphysik, ETH
    • , T. GreenshawAffiliated withDepartment of Physics, University of Liverpool
    • , M. GregoriAffiliated withQueen Mary and Westfield College
    • , B.R. GrellAffiliated withDESY
    • , G. GrindhammerAffiliated withMax-Planck-Institut für Physik
    • , S. HabibAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , D. HaidtAffiliated withDESY
    • , M. HanssonAffiliated withPhysics Department, University of Lund
    • , G. HeinzelmannAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , C. HelebrantAffiliated withDESY
    • , R.C.W. HendersonAffiliated withDepartment of Physics, University of Lancaster
    • , H. HenschelAffiliated withDESY
    • , G. HerreraAffiliated withDepartamento de Fisica, CINVESTAV
    • , M. HildebrandtAffiliated withPaul Scherrer Institut
    • , K.H. HillerAffiliated withDESY
    • , D. HoffmannAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee
    • , R. HorisbergerAffiliated withPaul Scherrer Institut
    • , A. HovhannisyanAffiliated withYerevan Physics Institute
    • , T. HreusAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit AntwerpenUniversity of P.J. Šafárik
    • , S. HussainAffiliated withQueen Mary and Westfield College
    • , M. JacquetAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , M.E. JanssenAffiliated withDESY
    • , X. JanssenAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , V. JemanovAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , L. JönssonAffiliated withPhysics Department, University of Lund
    • , D.P. JohnsonAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , A.W. JungAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , H. JungAffiliated withDESY
    • , M. KapichineAffiliated withJoint Institute for Nuclear Research
    • , J. KatzyAffiliated withDESY
    • , I.R. KenyonAffiliated withSchool of Physics and Astronomy, University of Birmingham
    • , C. KieslingAffiliated withMax-Planck-Institut für Physik
    • , M. KleinAffiliated withDESY
    • , C. KleinwortAffiliated withDESY
    • , T. KlimkovichAffiliated withDESY
    • , T. KlugeAffiliated withDESY
    • , G. KniesAffiliated withDESY
    • , A. KnutssonAffiliated withPhysics Department, University of Lund
    • , V. KorbelAffiliated withDESY
    • , P. KostkaAffiliated withDESY
    • , M. KraemerAffiliated withDESY
    • , K. KrastevAffiliated withDESY
    • , J. KretzschmarAffiliated withDESY
    • , A. KropivnitskayaAffiliated withInstitute for Theoretical and Experimental Physics
    • , K. KrügerAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , M.P.J. LandonAffiliated withQueen Mary and Westfield College
    • , W. LangeAffiliated withDESY
    • , G. Laštovička-MedinAffiliated withFaculty of Science, University of Montenegro
    • , P. LaycockAffiliated withDepartment of Physics, University of Liverpool
    • , A. LebedevAffiliated withLebedev Physical Institute
    • , G. LeibenguthAffiliated withInstitut für Teilchenphysik, ETH
    • , V. LendermannAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , S. LevonianAffiliated withDESY
    • , L. LindfeldAffiliated withPhysik-Institut der Universität Zürich
    • , K. LipkaAffiliated withDESY
    • , A. LiptajAffiliated withMax-Planck-Institut für Physik
    • , B. ListAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , J. ListAffiliated withDESY
    • , N. LoktionovaAffiliated withLebedev Physical Institute
    • , R. Lopez-FernandezAffiliated withDepartamento de Fisica, CINVESTAV
    • , V. LubimovAffiliated withInstitute for Theoretical and Experimental Physics
    • , A.-I. Lucaci-TimoceAffiliated withDESY
    • , H. LuedersAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , L. LytkinAffiliated withMax-Planck-Institut für Kernphysik
    • , A. MakankineAffiliated withJoint Institute for Nuclear Research
    • , E. MalinovskiAffiliated withLebedev Physical Institute
    • , P. MarageAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , L. MartiAffiliated withDESY
    • , M. MartisikovaAffiliated withDESY
    • , H.-U. MartynAffiliated withI. Physikalisches Institut der RWTH
    • , S.J. MaxfieldAffiliated withDepartment of Physics, University of Liverpool
    • , A. MehtaAffiliated withDepartment of Physics, University of Liverpool
    • , K. MeierAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , A.B. MeyerAffiliated withDESY
    • , H. MeyerAffiliated withDESY
    • , H. MeyerAffiliated withFachbereich C, Universität Wuppertal
    • , J. MeyerAffiliated withDESY
    • , V. MichelsAffiliated withDESY
    • , S. MikockiAffiliated withInstitute for Nuclear Physics
    • , I. Milcewicz-MikaAffiliated withInstitute for Nuclear Physics
    • , D. MladenovAffiliated withInstitute for Nuclear Research and Nuclear Energy
    • , A. MohamedAffiliated withDepartment of Physics, University of Liverpool
    • , F. MoreauAffiliated withLLR, Ecole Polytechnique, IN2P3-CNRS
    • , A. MorozovAffiliated withJoint Institute for Nuclear Research
    • , J.V. MorrisAffiliated withRutherford Appleton Laboratory, Chilton
    • , M.U. MozerAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , K. MüllerAffiliated withPhysik-Institut der Universität Zürich
    • , P. MurínAffiliated withInstitute of Experimental Physics, Slovak Academy of SciencesUniversity of P.J. Šafárik
    • , K. NankovAffiliated withInstitute for Nuclear Research and Nuclear Energy
    • , B. NaroskaAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , T. NaumannAffiliated withDESY
    • , P.R. NewmanAffiliated withSchool of Physics and Astronomy, University of Birmingham
    • , C. NiebuhrAffiliated withDESY
    • , A. NikiforovAffiliated withMax-Planck-Institut für Physik
    • , G. NowakAffiliated withInstitute for Nuclear Physics
    • , K. NowakAffiliated withPhysik-Institut der Universität Zürich
    • , M. NozickaAffiliated withDESY
    • , R. OganezovAffiliated withYerevan Physics Institute
    • , B. OlivierAffiliated withMax-Planck-Institut für Physik
    • , J.E. OlssonAffiliated withDESY
    • , S. OsmanAffiliated withPhysics Department, University of Lund
    • , D. OzerovAffiliated withInstitute for Theoretical and Experimental Physics
    • , V. PalichikAffiliated withJoint Institute for Nuclear Research
    • , I. PanagouliasAffiliated withDESYPhysics Department, National Technical University
    • , M. PandurovicAffiliated withVinca Institute of Nuclear Sciences
    • , T. PapadopoulouAffiliated withDESYPhysics Department, National Technical University
    • , C. PascaudAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , G.D. PatelAffiliated withDepartment of Physics, University of Liverpool
    • , H. PengAffiliated withDESY
    • , E. PerezAffiliated withCEA, DSM/DAPNIA, CE-Saclay
    • , D. Perez-AstudilloAffiliated withDepartamento de Fisica Aplicada, CINVESTAV
    • , A. PerieanuAffiliated withDESY
    • , A. PetrukhinAffiliated withInstitute for Theoretical and Experimental Physics
    • , I. PicuricAffiliated withFaculty of Science, University of Montenegro
    • , S. PiecAffiliated withDESY
    • , D. PitzlAffiliated withDESY
    • , R. PlačakytėAffiliated withDESY
    • , B. PovhAffiliated withMax-Planck-Institut für Kernphysik
    • , T. PredaAffiliated withDESYNational Institute for Physics and Nuclear Engineering, Magurele
    • , P. PrideauxAffiliated withDepartment of Physics, University of Liverpool
    • , A.J. RahmatAffiliated withDepartment of Physics, University of Liverpool
    • , N. RaicevicAffiliated withFaculty of Science, University of Montenegro
    • , T. RavdandorjAffiliated withInstitute of Physics and Technology of the Mongolian Academy of Sciences
    • , P. ReimerAffiliated withInstitute of Physics, Academy of Sciences of the Czech Republic
    • , A. RimmerAffiliated withDepartment of Physics, University of Liverpool
    • , C. RislerAffiliated withDESY
    • , E. RizviAffiliated withQueen Mary and Westfield College
    • , P. RobmannAffiliated withPhysik-Institut der Universität Zürich
    • , B. RolandAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , R. RoosenAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , A. RostovtsevAffiliated withInstitute for Theoretical and Experimental Physics
    • , Z. RurikovaAffiliated withDESY
    • , S. RusakovAffiliated withLebedev Physical Institute
    • , F. SalvaireAffiliated withDESY
    • , D.P.C. SankeyAffiliated withRutherford Appleton Laboratory, Chilton
    • , M. SauterAffiliated withInstitut für Teilchenphysik, ETH
    • , E. SauvanAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee
    • , S. SchmidtAffiliated withDESY
    • , S. SchmittAffiliated withDESY
    • , C. SchmitzAffiliated withPhysik-Institut der Universität Zürich
    • , L. SchoeffelAffiliated withCEA, DSM/DAPNIA, CE-Saclay
    • , A. SchöningAffiliated withInstitut für Teilchenphysik, ETH
    • , H.-C. Schultz-CoulonAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , F. SefkowAffiliated withDESY
    • , R.N. Shaw-WestAffiliated withSchool of Physics and Astronomy, University of Birmingham
    • , I. SheviakovAffiliated withLebedev Physical Institute
    • , L.N. ShtarkovAffiliated withLebedev Physical Institute
    • , T. SloanAffiliated withDepartment of Physics, University of Lancaster
    • , I. SmiljanicAffiliated withVinca Institute of Nuclear Sciences
    • , P. SmirnovAffiliated withLebedev Physical Institute
    • , Y. SolovievAffiliated withLebedev Physical Institute
    • , D. SouthAffiliated withInstitut für Physik, Universität Dortmund
    • , V. SpaskovAffiliated withJoint Institute for Nuclear Research
    • , A. SpeckaAffiliated withLLR, Ecole Polytechnique, IN2P3-CNRS
    • , M. StederAffiliated withDESY
    • , B. StellaAffiliated withDipartimento di Fisica Università di Roma Tre and INFN Roma 3
    • , J. StieweAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , U. StraumannAffiliated withPhysik-Institut der Universität Zürich
    • , D. SunarAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , T. SykoraAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , V. TchoulakovAffiliated withJoint Institute for Nuclear Research
    • , G. ThompsonAffiliated withQueen Mary and Westfield College
    • , P.D. ThompsonAffiliated withSchool of Physics and Astronomy, University of Birmingham
    • , T. TollAffiliated withDESY
    • , F. TomaszAffiliated withInstitute of Experimental Physics, Slovak Academy of Sciences
    • , D. TraynorAffiliated withQueen Mary and Westfield College
    • , T.N. TrinhAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee
    • , P. TruölAffiliated withPhysik-Institut der Universität Zürich
    • , I. TsakovAffiliated withInstitute for Nuclear Research and Nuclear Energy
    • , B. TseepeldorjAffiliated withInstitute of Physics and Technology of the Mongolian Academy of Sciences
    • , G. TsipolitisAffiliated withDESYPhysics Department, National Technical University
    • , I. TsurinAffiliated withDESY
    • , J. TurnauAffiliated withInstitute for Nuclear Physics
    • , E. TzamariudakiAffiliated withMax-Planck-Institut für Physik
    • , K. UrbanAffiliated withKirchhoff-Institut für Physik, Universität Heidelberg
    • , A. UsikAffiliated withLebedev Physical Institute
    • , D. UtkinAffiliated withInstitute for Theoretical and Experimental Physics
    • , A. ValkárováAffiliated withFaculty of Mathematics and Physics, Charles University
    • , C. ValléeAffiliated withCPPM, CNRS/IN2P3 – Univ. Mediterranee
    • , P. Van MechelenAffiliated withInter-University Institute for High Energies ULB-VUBUniversiteit Antwerpen
    • , A. Vargas TrevinoAffiliated withDESY
    • , Y. VazdikAffiliated withLebedev Physical Institute
    • , S. VinokurovaAffiliated withDESY
    • , V. VolchinskiAffiliated withYerevan Physics Institute
    • , K. WackerAffiliated withInstitut für Physik, Universität Dortmund
    • , G. WeberAffiliated withInstitut für Experimentalphysik, Universität Hamburg
    • , R. WeberAffiliated withInstitut für Teilchenphysik, ETH
    • , D. WegenerAffiliated withInstitut für Physik, Universität Dortmund
    • , C. WernerAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , M. WesselsAffiliated withDESY
    • , C. WissingAffiliated withDESY
    • , R. WolfAffiliated withPhysikalisches Institut, Universität Heidelberg
    • , E. WünschAffiliated withDESY
    • , S. XellaAffiliated withPhysik-Institut der Universität Zürich
    • , W. YanAffiliated withDESY
    • , V. YeganovAffiliated withYerevan Physics Institute
    • , J. ŽáčekAffiliated withFaculty of Mathematics and Physics, Charles University
    • , J. ZálešákAffiliated withInstitute of Physics, Academy of Sciences of the Czech Republic
    • , Z. ZhangAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , A. ZhelezovAffiliated withInstitute for Theoretical and Experimental Physics
    • , A. ZhokinAffiliated withInstitute for Theoretical and Experimental Physics
    • , Y.C. ZhuAffiliated withDESY
    • , J. ZimmermannAffiliated withMax-Planck-Institut für Physik
    • , T. ZimmermannAffiliated withInstitut für Teilchenphysik, ETH
    • , H. ZohrabyanAffiliated withYerevan Physics Institute
    • , F. ZomerAffiliated withLAL, Université de Paris-Sud 11, IN2P3-CNRS
    • , The H1 Collaboration

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Abstract

A search for the lepton flavour violating processes ep→μX and ep→τX is performed with the H1 experiment at HERA. Final states with a muon or tau and a hadronic jet are searched for in a data sample corresponding to an integrated luminosity of 66.5 pb-1 for e+p collisions and 13.7 pb-1 for e-p collisions at a centre-of-mass energy of 319 GeV. No evidence for lepton flavour violation is found. Limits are derived on the mass and the couplings of leptoquarks inducing lepton flavour violation in an extension of the Buchmüller–Rückl–Wyler effective model. Leptoquarks produced in ep collisions with a coupling strength of λ=0.3 and decaying with the same coupling strength to a muon–quark pair or a tau–quark pair are excluded at 95% confidence level up to masses of 459 GeV and 379 GeV, respectively.