Abstract
Searches for unstable neutral and charged heavy leptons (L0, L±) have been performed using a data sample of 10.0 pb-1 at a centre-of-mass energy of √s = 161.3 GeV collected with the OPAL detector at LEP during July and August 1996. Two candidate events were observed after the selection, which is consistent with the expected total background of 1.57 events, and lower limits have been derived on heavy lepton masses for various models. If an unstable Dirac neutral heavy lepton, L0, decays only into eW*, μW* or τW*, the lower limits on its mass at the 95% C.L. are 69.3 GeV, 72.0 GeV and 66.0 GeV, respectively. The limits are modified for a Majorana L0 to 59.5 GeV, 60.5 GeV and 55.7 GeV, respectively. If an unstable heavy charged lepton, L±, decays into a stable heavy neutrino, and if mL± - mvL > 13 GeV, a lower limit on its mass of 73.5 GeV is obtained. If the L± decays through lepton flavour mixing into a massless neutrino vℓ and W*±, the lower limit on mL± was determined to be 76.7 GeV at 95% C.L.
Original language | English |
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Pages (from-to) | 217-230 |
Number of pages | 14 |
Journal | Physics Letters B |
Volume | 393 |
Issue number | 1-2 |
DOIs | |
State | Published - Feb 6 1997 |
Externally published | Yes |
Funding
We particularly wish to thank the SL Division for the efficient operation of the LEP acceleratora t the new energy of fi = 161 GeV and for their continuing close cooperation with our experimental group. We thank our colleagues from CEA, DAPNIA/SPP, CE-Saclay for their efforts over the years on the time-of-flight and trigger systems which we continue to use. We also thank Francesca Borzumati of the Weizmann Institute for her strong theoreticals upport. In addition to the support staff at our own institutions we are pleased to acknowledget he Departmento f Energy, USA, National Science Foundation, USA, Research Corporation, USA, Particle Physics and Astronomy Research Council, UK. Natural Sciences and Engineering Research Council, Canada, Israel Science Foundation, administeredb y the Israel Academy of Science and Humanities, Minerva Gesellschaft, Japanese Ministry of Education, Science and Culture (the Monbusho) and a grant under the Monbusho International Science ResearchP rogram. German Israeli Bi-national Science Foundation (GIF), Bundesministerium fiir Bildung, Wissenschaft, Forschung und Technologie, Germany, National ResearchC ouncil of Canada, Hungarian Foundation for Scientific Research,O TKA T-01 6660, and OTKA F-01 5089.
Funders | Funder number |
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German Israeli Bi-national Science Foundation | |
Hungarian Foundation for Scientific Research | O TKA T-01 6660 |
Minerva Gesellschaft | |
Monbusho International Science ResearchP rogram | |
National ResearchC ouncil of Canada | |
Natural Sciences and Engineering Research Council of Canada | |
Ministry of Education, Culture, Sports, Science and Technology | |
Hungarian Scientific Research Fund | F-01 5089 |
Israel Academy of Sciences and Humanities | |
Israel Science Foundation | |
Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie |