Using the ZEUS detector at the HERA electron-proton collider, we have searched for lepton flavor violation in ep collisions at a center-of-mass energy (√s) of 300 GeV. Events of the type e + p → ℓ + X with a final-state lepton of high transverse momentum, ℓ = μ or τ, were sought. No evidence was found for lepton flavor violation in the combined 1993 and 1994 data samples, for which the integrated luminosities were 0.84 pb-1 for e-p collisions and 2.94 pb-1 for e+p collisions. Limits on coupling vs. mass are provided for leptoquarks and R-parity violating squarks. For flavor violating couplings of electromagnetic strength, we set 95% confidence level lower limits on leptoquark masses between 207 GeV and 272 GeV, depending on the leptoquark species and final-state lepton. For leptoquark masses larger than 300 GeV, limits on flavor-changing couplings are determined, many of which supersede prior limits from rare decay processes.
Bibliographical noteFunding Information:
1 In the following, “electron” is generically used to denote both electrons and positrons 2 Though the threshold for top (t) quark production is below the HERA center–of–mass energy, with present luminosities t production would only be observable if the couplings were very large. Therefore, we choose not to report on LFV couplings involving top in this paper 29 also at University of Hamburg, Alexander von Humboldt Research Award 30 now at Lawrence Berkeley Laboratory, Berkeley 31 now at Yale University, New Haven, CT 32 supported by a MINERVA Fellowship 33 supported by the Japan Society for the Promotion of Science (JSPS) 34 present address: Tokyo Metropolitan College of Allied Medical Sciences, Tokyo 116, Japan 35 supported by the Polish State Committee for Scientific Research, grant No. 2P03B09308 36 supported by the Polish State Committee for Scientific Research, grant No. 2P03B09208 37 now at TECMAR Incorporated, Toronto a supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) b supported by the FCAR of Québec, Canada c supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF), under contract numbers 057BN19P, 057FR19P, 057HH19P, 057HH29P, 057SI75I d supported by the MINERVA Gesellschaft für Forschung GmbH, the Israel Academy of Science and the U.S.-Israel Binational Science Foundation e supported by the German Israeli Foundation, and by the Israel Academy of Science f supported by the Italian National Institute for Nuclear Physics (INFN) g supported by the Japanese Ministry of Education, Science and Culture (the Monbusho) and its grants for Scientific Research h supported by the Korean Ministry of Education and Korea Science and Engineering Foundation i supported by the Netherlands Foundation for Research on Matter (FOM) j supported by the Polish State Committee for Scientific Research, grants No. 115/E-343/SPUB/P03/109/95, 2P03B 244 08p02, p03, p04 and p05, and the Foundation for Polish-German Collaboration (proj. No. 506/92) k supported by the Polish State Committee for Scientific Research (grant No. 2 P03B 083 08) and Foundation for Polish-German Collaboration l partially supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF) m supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF), and the Fund of Fundamental Research of Russian Ministry of Science and Education and by INTAS-Grant No. 93-63 n supported by the Spanish Ministry of Education and Science through funds provided by CICYT o supported by the Particle Physics and Astronomy Research Council p supported by the US Department of Energy q supported by the US National Science Foundation Fig. 1. The (a) s–, (b) u–, and (c) t–channel Feynman diagrams for LFV. For the s–channel and u–channel diagrams, we denote the couplings as λℓq, where the indices refer to the lepton and quark flavors
15 visitor from Florida State University 16 now at DESY Computer Center 17 supported by European Community Program PRAXIS XXI 18 present address: Dipartimento di Fisica, Univ. “La Sapienza”, Rome 19 now at ATLAS Collaboration, Univ. of Munich 20 now at Star Division Entwicklungs-und Vertriebs-GmbH, Hamburg 21 now at Philips Medizin Systeme, Hamburg 22 also supported by NSERC, Canada 23 supported by an EC fellowship 24 PPARC Post-doctoral Fellow 25 now at Park Medical Systems Inc., Lachine, Canada 26 partially supported by DESY 27 now at Philips Natlab, Eindhoven, NL 28 now at Department of Energy, Washington
1 also at IROE Florence, Italy 2 now at Univ. of Salerno and INFN Napoli, Italy 3 supported by Worldlab, Lausanne, Switzerland 4 now at Univ. of California, Santa Cruz 5 now a self-employed consultant 6 now at VDI-Technologiezentrum Düsseldorf 7 now at Commasoft, Bonn 8 also at University of Torino and Alexander von Humboldt Fellow 9 Alexander von Humboldt Fellow 10 Alfred P. Sloan Foundation Fellow 11 now at University of Washington, Seattle 12 now at California Institute of Technology, Los Angeles 13 supported by an EC fellowship number ERBFMBICT 950172 14 now at Inst. of Computer Science, Jagellonian Univ., Cracow
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)