A DIRECT SEARCH FOR NEW CHARGED HEAVY LEPTONS AT LEP

This is the post-print version of the Article - Copyright @ 1990 ElsevierResults are presented from a search for a new charged heavy lepton in e+e− annihilation. The data were taken with the OPAL detector at LEP during a scan of the Z0 resonance. Two independent search techniques were used, one looking for events with large missing energy and missing momentum transverse to the beam, and the other for events with isolated energetic leptons. Two candidate events, consistent with expected background, were found in the first search; none was found in the second. These results allow the exclusion at the 95% confidence level of a charged heavy lepton of mass less than 44.3 GeV/c2 if it is assumed to have a massless neutrino partner. Limits are also presented for the case of a massive neutrino.This study is supported by The Bundesministerium f'tir Forschung und Technologie, FRG, The Department of Energy, USA, The Institut de Recherche Fondamentale du Commissariat a l'Energie Atomique, The Israeli Ministry of Science, The Minerva Gesellschaft, The National Science Foundation, USA, The Natural Sciences and Engineering Research Council, Canada, The Japanese Ministry of Education, Science and Culture (the Monbusho) and a grant under the Monbusho International Science Research Program, The Science and Engineering Research Council, UK and The A.P. Sloan Foundation

A direct search for neutralino production at LEP

This is the post-print version of the Article - Copyright @ 1990 Elsevier.A search has been performed for the production of neutralinos (χ, χ′) in e+e− annihilation at energies near the Z0 pole. No evidence for these particles was found either in searches for events with two acoplanar jets, low visible energy, and missing pt (sensitive to or in searches for single-photon events (sensitive to Z0→χχ′→χχγ). Model independent upper limits (at the 95% CL) on the branching ratio for the decay mode Z0 →χχ′ of a few 10−4 are obtained for most of the range of neutralino masses that is kinematically accessible at LEP energies. Upper limits on the mixing factor of neutralinos are also placed as a function of the neutralino masses.This study was supported by the US Dept. of Energy, US National Science Foundation, UK Science and Engineering Research Council, the A.P. Sloan Foundation, the Canadian National Sciences and Engineering Research Council, the Israeli Ministry of Science, Minerva Gesellschaft, The Japanese Ministry of Education, Science and Culture, the Monbusho International Science Research Program, the American-Israeli Bi-national Science Foundation, L'insitut de Recherche Fondamentale du Comissariat a L'Energie Atomique, and the Bundesministerium fur Forschng und Technologie