1,129 research outputs found

    Study of ZZ production at LEP at sqrt(s) = 183 - 209 GeV

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    A study of Z boson pair production in e+e- annihilation using the OPAL detector at LEP is reported. The ZZ production cross-section is measured, limits on anomalous ZZgamma and ZZZ couplings are derived, and constraints on models of low scale quantum gravity in extra spatial dimensions are set.Comment: 4 pages, 4 figures. To be published in the Proceedings of DPF2000, The Meeting of The Division of Particles and Fields of The American Physical Society, Columbus, Ohio, 9-12 August 2000, (Supplement of the International Journal of Modern Physics A (IJMP)

    Search for supersymmetry, extra dimensions and exotic phenomena at LEP

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    The latest results on searches for supersymmetry, extra dimensions and exotic phenomena from the LEP collaborations are presented. No significant signal-like excess is observed in the data. The results are interpreted in various models and robust constraints are placed.Comment: Contributed to 16th Les Rencontres de Physique de la Vallee d'Aoste: Results and Perspectives in Particle Physics, La Thuile, Aosta Valley, Italy, 3-9 Mar 200

    Search for SM and MSSM Higgs Bosons at LEP

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    Latest results from the LEP Collaboration on searches for neutral Higgs bosons predicted by the Standard Model and its minimal supersymmetric extension, the MSSM, are summarized.Comment: Talk presented at SUSY 2003: Supersymmetry in the Desert, University of Arizona, Tucson, AZ, June 5-10, 200

    The CMS Silicon Strip Tracker

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    The CMS collaboration is constructing the largest silicon tracker ever built with an active silicon area of 200 m^2 to provide robust charged particle tracking and vertex reconstruction within the 4T magnetic field of the CMS Solenoid. The design of the detector, the status of the construction and the performance of the substructures are reviewed.Comment: Presented at PANIC05, Particles and Nuclei International Conference, Santa Fe, New Mexico, USA, 24-28 October, 200

    Search for Gauginos and Gauge Mediated SUSY Breaking Scenarios at LEP

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    Data collected by the OPAL detector at LEP up to the highest energies of 209 GeV are analyzed to search for evidence of supersymmetric (SUSY) particle production. Chargino pair-production and neutralino associated production are considered in models where supersymmetry breaking is mediated by gravitational interactions. The focus of the searches is on topologies arising when scalar fermions are heavy and the lightest neutralino is the lightest SUSY particle (LSP). Searches for topologies predicted by gauge-mediated SUSY breaking (GMSB) models are also discussed. In these models the LSP is the gravitino and the phenomenology is driven by the nature of the next-to-lightest SUSY particle (NLSP) which is either the lightest neutralino, stau or mass degenerate sleptons. As the NLSP decay length is effectively unconstrained, all possible values are considered and results independent of the NLSP lifetime are presented for all relevant final states including direct NLSP pair-production and NLSP production via cascade decays of heavier SUSY particles. None of the searches shows evidence for SUSY particle production. Cross-section limits are presented at the 95% confidence level both for direct NLSP production and, for the first time, also for cascade decays. These are then interpreted in the framework of minimal theoretical models. Large areas of the accessible parameter space are excluded and constraints on the mass of the SUSY particles are derived.Comment: Presented at HEP2005 International Europhysics Conference on High Energy Physics, July 21st - 27th 2005, Lisboa, Portugal (4 pages, 6 figures

    Exploring New Physics Through Contact Interactions in Lepton Pair Production at a Linear Collider

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    If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV - 1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.Comment: Contributed to APS / DPF / DPB Summer Study on the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun - 21 Jul 200

    Report of the Snowmass Subgroup on Extra Dimensions

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    In this report we summarize the work performed at Snowmass 2001 on the physics of extra dimensions. We divide these analyses into the following classes: searches for extra dimensional phenomena, identification of specific new physics scenarios, studies of black hole production and non-commutative QED.Comment: Contributed to APS / DPF / DPB Summer Study on the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun - 21 Jul 200

    The LEP Testimony: Exotic Searches and Studies

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    A selection of recent results on searches for phenomena beyond the Standard Model is presented from the LEP Collaborations, based on the data collected up to the highest centre-of-mass energies of 209 GeV.A selection of recent results on searches for phenomena beyond the Standard Model is presented from the LEP Collaborations, based on the data collected up to the highest centre-of-mass energies of 209 GeV

    Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

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    Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV