Isolated electrons and muons in events with missing transverse momentum at HERA
V. AndreevLebedev Physical Institute, Moscow, Russia 5B. AndrieuLaboratoire de Physique Nucléaire et de Hautes ÉnergiesT. AnthonisUniversity of Antwerp, Antwerp, BelgiumA. AstvatsatourovDESY, Zeuthen, GermanyA. BabaevInstitute for Theoretical and Experimental Physics, Moscow, Russia 15J. BährDESY, Zeuthen, GermanyP. BaranovLebedev Physical Institute, Moscow, Russia 5E. BarreletLaboratoire de Physique Nucléaire et de Hautes ÉnergiesW. BartelS. BaumgartnerInstitut für Teilchenphysik, ETH, Zürich, Switzerland 17J. BeckerPhysik-Institut der Universität Zürich, Zürich, Switzerland 17M. BeckinghamPhysics Department, University of Manchester, Manchester, UK 10A. BeglarianYerevan Physics Institute, Yerevan, ArmeniaO. BehnkePhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 9A. BelousovLebedev Physical Institute, Moscow, Russia 5Ch. BergerI. Physikalisches Institut der RWTH, Aachen, Germany 9T. BerndtKirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany 9J.C. BizotLAL, Université de Paris-Sud, IN2P3-CNRS, Orsay, FranceJ. BöhmeV. BoudryLPNHE, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceJ. BraciníkMax Planck Institute for PhysicsW. BraunschweigI. Physikalisches Institut der RWTH, Aachen, Germany 9V. BrissonUniversité Paris Cité, Paris, FranceH.-B. BrökerIII. Physikalisches Institut der RWTH, Aachen, Germany 9Dunstan BrownD. BrunckoSlovak Academy of Sciences, Bratislava, SlovakiaF.W. BüsserInstitut für Experimentalphysik, Universität Hamburg, Hamburg, Germany 9A. BunyatyanYerevan Physics Institute, Yerevan, ArmeniaA. BurrageDepartment of Physics, University of Liverpool, Liverpool, UK 10G. BuschhornMax Planck Society, Munich, GermanyL. BystritskayaInstitute for Theoretical and Experimental Physics, Moscow, Russia 15A.J. CampbellS. CaronI. Physikalisches Institut der RWTH, Aachen, Germany 9F. Cassol-BrunnerCentre National de la Recherche Scientifique, Paris, FranceV. ChekelianMax-Planck-Institut für Physik, München, GermanyD. ClarkeRutherford Appleton Laboratory, Chilton, Didcot, UK 10C. CollardUniversity of Antwerp, Antwerp, BelgiumJ.G. ContrerasInstitut für Physik, Universität Dortmund, Dortmund, Germany 9Y.R. CoppensSchool of Physics and Space Research, University of Birmingham, Birmingham, UKJ. A. CoughlanRutherford Appleton Laboratory, Chilton, Didcot, UK 10M.-C. CousinouCentre National de la Recherche Scientifique, Paris, FranceB. CoxPhysics Department, University of Manchester, Manchester, UK 10G. CozzikaDSM (Netherlands), Heerlen, NetherlandsJ. CvachInstitute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic 5 16J.B. DaintonDepartment of Physics, University of Liverpool, Liverpool, UK 10W.D. DauInstitut für experimentelle und Angewandte Physik, Universität Kiel, Kiel, GermanyK. DaumFachbereich Physik, Bergische Universität Gesamthochschule Wuppertal, Wuppertal, GermanyMarcus DavidssonPhysics Department, University of Lund, Lund, Sweden 14B. DelcourtUniversité Paris Cité, Paris, FranceNicolas DelerueCentre National de la Recherche Scientifique, Paris, FranceR. DemirchyanYerevan Physics Institute, Yerevan, ArmeniaA. De RoeckDESY, Hamburg, GermanyE. A. De WolfUniversity of Antwerp, Antwerp, BelgiumC. DiaconuCentre National de la Recherche Scientifique, Paris, FranceJ. DingfelderPhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 9P. DixonQueen Mary and Westfield College, London, UK 10V. DodonovMax Planck Institute for Nuclear PhysicsJ.D. DowellSchool of Physics and Space Research, University of Birmingham, Birmingham, UKA. DubakMax Planck Society, Munich, GermanyC. DuprelIII. Physikalisches Institut der RWTH, Aachen, Germany 9G. EckerlinV. EfremenkoLaboratoire de Physique Nucléaire et de Hautes ÉnergiesS. EgliPaul Scherrer Institut, Villigen, SwitzerlandR. EichlerLaboratoire de Physique Nucléaire et de Hautes ÉnergiesF. EiselePhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 9M. EllerbrockPhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 9E. ElsenM. ErdmannPeter FaulknerInstitute for Nuclear Physics, Cracow, PolandL. FavartUniversity of Antwerp, Antwerp, BelgiumA. FedotovInstitute for Theoretical and Experimental Physics, Moscow, Russia 15R. FelstLaboratoire de Physique Nucléaire et de Hautes ÉnergiesJ. FerenceiS. FerronLPNHE, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceM. FleischerP. FleischmannDESY, Hamburg, GermanyY.H. FlemingInstitute for Nuclear Physics, Cracow, PolandG. FluckeDESY, Hamburg, GermanyG. FlüggeIII. Physikalisches Institut der RWTH, Aachen, Germany 9A. FomenkoLebedev Physical Institute, Moscow, Russia 5I. ForestiPhysik-Institut der Universität Zürich, Zürich, Switzerland 17J. FormánekFaculty of Mathematics and Physics, Charles University, Praha, Czech Republic 5 16G. FrankeDESY, Hamburg, GermanyG. FrisingI. Physikalisches Institut der RWTH, Aachen, Germany 9E. GabathulerDepartment of Physics, University of Liverpool, Liverpool, UK 10K. GabathulerPaul Scherrer Institut, Villigen, SwitzerlandJ. GarveySchool of Physics and Space Research, University of Birmingham, Birmingham, UK 10J. GassnerPaul Scherrer Institut, Villigen, SwitzerlandJ. GaylerR. GerhardsLaboratoire de Physique Nucléaire et de Hautes ÉnergiesC. GerlichPhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 9S. GhazaryanYerevan Physics Institute, Yerevan, ArmeniaL. GoerlichInstitute for Nuclear Physics, Cracow, PolandN. GogitidzeLebedev Physical Institute, Moscow, Russia 5S. GorbounovInstitute for Nuclear Physics, Cracow, PolandC. GrabSwiss National Science Foundation, Bern, SwitzerlandVarlen GrabskiYerevan Physics Institute, Yerevan, ArmeniaH. GrässlerIII. Physikalisches Institut der RWTH, Aachen, Germany 9
2003en
ABI
Аннотация
A search for events with a high-energy isolated electron or muon and missing transverse momentum has been performed at the electron–proton collider HERA using an integrated luminosity of 13.6 pb −1 in e − p scattering and 104.7 pb −1 in e + p scattering. Within the Standard Model such events are expected to be mainly due to W boson production with subsequent leptonic decay. In e − p interactions one event is observed in the electron channel and none in the muon channel, consistent with the expectation of the Standard Model. In the e + p data a total of 18 events are seen in the electron and muon channels compared to an expectation of 12.4±1.7 dominated by W production (9.4±1.6). Whilst the overall observed number of events is broadly in agreement with the number predicted by the Standard Model, there is an excess of events with transverse momentum of the hadronic system greater than 25 GeV with 10 events found compared to 2.9±0.5 expected. The results are used to determine the cross-section for events with an isolated electron or muon and missing transverse momentum.
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