Abstract

A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy leptons are considered. No evidence for their existence is found and lower limits on their masses are set.

Highlights

  • Many theories beyond the Standard Model of the electro-weak interactions [1] predict the existence of new heavy leptons [2] with observable production cross sections and cleanly identifiable final states

  • The main difference between pair-produced Dirac and Majorana neutral heavy leptons is the dependence of the cross section on their velocity β

  • The mean decay length, D, as a function of |U |2 and mass is given by D = βγ cτL ∝ β|U |−2mαL [11], where τL is the lifetime of the heavy lepton and α ≈ −6

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Summary

27 September 2001

P. Achard t, O. Adriani q, M. Aguilar-Benitez x, J. Alcaraz x,r, G. Alemanni v, J. Allaby r, A. Aloisio ab, M.G. Alviggi ab, H. Anderhub au, V.P. Andreev f,ag, F. Anselmo i, A. Arefiev aa, T. Azemoon c, T. Aziz j,r, M. Baarmand y, P. Bagnaia al, A. Bajo x, G. Baksay p, L. Baksay y, S.V. Baldew b, S. Banerjee j, Sw. Banerjee d, A. Barczyk au,as, R. Barillère r, P. Bartalini v, M. Basile i, N. Batalova ar, R. Battiston af, A. Bay v, F. Becattini q, U. Becker n, F. Behner au, L. Bellucci q, R. Berbeco c, J. Berdugo x, P. Berges n, B. Bertucci af, B.L. Betev au, M. Biasini af, A. Biland au, J.J. Blaising d, S.C. Blyth ah, G.J. Bobbink b, A. Böhm a, L. Boldizsar m, B. Borgia al, D. Bourilkov au, M. Bourquin t, S. Braccini t, J.G. Branson an, F. Brochu d, A. Buijs aq, J.D. Burger n, W.J. Burger af, X.D. Cai n, M. Capell n, G. Cara Romeo i, G. Carlino ab, A. Cartacci q, J. Casaus x, F. Cavallari al, N. Cavallo ai, C. Cecchi af, M. Cerrada x, M. Chamizo t, Y.H. Chang aw, M. Chemarin w, A. Chen aw, G. Chen g, G.M. Chen g, H.F. Chen u, H.S. Chen g, G. Chiefari ab, L. Cifarelli am, F. Cindolo i, I. Clare n, R. Clare ak, G. Coignet d, N. Colino x, S. Costantini al, B. de la Cruz x, S. Cucciarelli af, T.S. Dai n, J.A. van Dalen ad, R. de Asmundis ab, P. Déglon t, J. Debreczeni m, A. Degré d, K. Deiters as, D. della Volpe ab, E. Delmeire t, P. Denes aj, F. DeNotaristefani al, A. De Salvo au, M. Diemoz al, M. Dierckxsens b, D. van Dierendonck b, C. Dionisi al, M. Dittmar au,r, A. Doria ab, M.T. Dova k,5, D. Duchesneau d, P. Duinker b, B. Echenard t, A. Eline r, H. El Mamouni w, A. Engler ah, F.J. Eppling n, A. Ewers a, P. Extermann t, M.A. Falagan x, S. Falciano al, A. Favara r, J. Fay w, O. Fedin ag, M. Felcini au, T. Ferguson ah, H. Fesefeldt a, E. Fiandrini af, J.H. Field t, F. Filthaut ad, P.H. Fisher n, W. Fisher aj, I. Fisk an, G. Forconi n, K. Freudenreich au, C. Furetta z, Yu. Galaktionov aa,n, S.N. Ganguli j, P. Garcia-Abia e,r, M. Gataullin ae, S. Gentile al, S. 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Longo al, Y.S. Lu g, K. Lübelsmeyer a, C. Luci al, D. Luckey n, L. Luminari al, W. Lustermann au, W.G. Ma u, L. Malgeri t, A. Malinin aa, C. Maña x, D. Mangeol ad, J. Mans aj, J.P. Martin w, F. Marzano al, K. Mazumdar j, R.R. McNeil f, S. Mele r, L. Merola ab, M. Meschini q, W.J. Metzger ad, A. Mihul l, H. Milcent r, G. Mirabelli al, J. Mnich a, G.B. Mohanty j, G.S. Muanza w, A.J.M. Muijs b, B. Musicar an, M. Musy al, S. Nagy p, M. Napolitano ab, F. Nessi-Tedaldi au, H. Newman ae, T. Niessen a, A. Nisati al, H. Nowak at, R. Ofierzynski au, G. Organtini al, C. Palomares r, D. Pandoulas a, P. Paolucci ab, R. Paramatti al, G. Passaleva q, S. Patricelli ab, T. Paul k, M. Pauluzzi af, C. Paus n, F. Pauss au, M. Pedace al, S. Pensotti z, D. Perret-Gallix d, B. Petersen ad, D. Piccolo ab, F. Pierella i, P.A. Piroué aj, E. Pistolesi z, V. Plyaskin aa, M. Pohl t, V. Pojidaev q, H. Postema n, J. Pothier r, D.O. Prokofiev ar, D. Prokofiev ag, J. Quartieri am, G. 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Physikalisches Institut, RWTH, D-52056 Aachen, Germany 1 b National Institute for High Energy Physics, NIKHEF, and University of Amsterdam, NL-1009 DB Amsterdam, The Netherlands c University of Michigan, Ann Arbor, MI 48109, USA d Laboratoire d’Annecy-le-Vieux de Physique des Particules, LAPP, IN2P3-CNRS, BP 110, F-74941 Annecy-le-Vieux Cedex, France e Institute of Physics, University of Basel, CH-4056 Basel, Switzerland f Louisiana State University, Baton Rouge, LA 70803, USA g Institute of High Energy Physics, IHEP, 100039 Beijing, China 6 h Humboldt University, D-10099 Berlin, Germany 1 i University of Bologna and INFN-Sezione di Bologna, I-40126 Bologna, Italy j Tata Institute of Fundamental Research, Mumbai (Bombay) 400 005, India k Northeastern University, Boston, MA 02115, USA l Institute of Atomic Physics and University of Bucharest, R-76900 Bucharest, Romania m Central Research Institute for Physics of the Hungarian Academy of Sciences, H-1525 Budapest 114, Hungary 2 n Massachusetts Institute of Technology, Cambridge, MA 02139, USA o Panjab University, Chandigarh 160 014, India p KLTE-ATOMKI, H-4010 Debrecen, Hungary 3 q INFN, Sezione di Firenze, and University of Florence, I-50125 Florence, Italy r European Laboratory for Particle Physics, CERN, CH-1211 Geneva 23, Switzerland s World Laboratory, FBLJA Project, CH-1211 Geneva 23, Switzerland t University of Geneva, CH-1211 Geneva 4, Switzerland u Chinese University of Science and Technology, USTC, Hefei, Anhui 230 029, PR China 6 v University of Lausanne, CH-1015 Lausanne, Switzerland w Institut de Physique Nucléaire de Lyon, IN2P3-CNRS, Université Claude Bernard, F-69622 Villeurbanne, France x Centro de Investigaciones Energéticas, Medioambientales y Tecnologícas, CIEMAT, E-28040 Madrid, Spain 4 y Florida Institute of Technology, Melbourne, FL 32901, USA z INFN, Sezione di Milano, I-20133 Milan, Italy aa Institute of Theoretical and Experimental Physics, ITEP, Moscow, Russia ab INFN, Sezione di Napoli, and University of Naples, I-80125 Naples, Italy ac Department of Physics, University of Cyprus, Nicosia, Cyprus ad University of Nijmegen and NIKHEF, NL-6525 ED Nijmegen, The Netherlands ae California Institute of Technology, Pasadena, CA 91125, USA af INFN, Sezione di Perugia, and Università Degli Studi di Perugia, I-06100 Perugia, Italy ag Nuclear Physics Institute, St. Petersburg, Russia ah Carnegie Mellon University, Pittsburgh, PA 15213, USA ai INFN, Sezione di Napoli, and University of Potenza, I-85100 Potenza, Italy aj Princeton University, Princeton, NJ 08544, USA ak University of California, Riverside, CA 92521, USA al INFN, Sezione di Roma, and University of Rome, “La Sapienza”, I-00185 Rome, Italy am University and INFN, Salerno, I-84100 Salerno, Italy an University of California, San Diego, CA 92093, USA ao Bulgarian Academy of Sciences, Central Lab. of Mechatronics and Instrumentation, BU-1113 Sofia, Bulgaria ap The Center for High Energy Physics, Kyungpook National University, 702-701 Taegu, South Korea aq Utrecht University and NIKHEF, NL-3584 CB Utrecht, The Netherlands ar Purdue University, West Lafayette, IN 47907, USA as Paul Scherrer Institut, PSI, CH-5232 Villigen, Switzerland at DESY, D-15738 Zeuthen, Germany au Eidgenössische Technische Hochschule, ETH Zürich, CH-8093 Zürich, Switzerland av University of Hamburg, D-22761 Hamburg, Germany aw National Central University, Chung-Li, Taiwan, ROC ax Department of Physics, National Tsing Hua University, Taiwan, ROC Received 16 July 2001; received in revised form 6 August 2001; accepted 7 August 2001 Editor: L. Rolandi

Introduction
Production and decay of exotic leptons
Event simulation
Lepton and jet identification
Search for unstable neutral heavy leptons
Search for unstable charged heavy leptons
Search for stable charged heavy leptons
Results
Full Text
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