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Recherche de sélectrons et de smuons dans l'expérience DELPHI au LEP

Abstract : The main topic of this Thesis is the minimal supersymmetric extension of the Standard Model (MSSM). In the first part, we reanalyze the results of the chargino searches at LEP (on the basis of the DELPHI 189 GeV data sample) including the possibility of complex MSSM parameters. We study how they affect the present limits and how these limits are restored by the use of the experimental upper limit on the electric dipole moment of electron. In the second part, we use the Helicity Amplitude Method for cross section calculation. With this technique, we evaluate the main supersymmetric particle production cross sections at leptonic colliders. We also show how the spin correlations are important when one attempts to evaluate the MSSM parameters, using the angular distribution of final particles. In the last section, an analysis for selectron and smuon searches with the DELPHI detector at LEP is presented. To extract the selectron and smuon signal (two acoplanar electrons or muons of opposite charge) from the Standard Model background (W+W- and gamma gamma processes), we develop an analysis based on a Neural Network for each selectron and smuon mass hypothesis. The analysis of data for a center of mass energy from 184 to 202 GeV, for an equivalent integrated luminosity of 440 pb-1 , did not show any significant deviation of the number of events from the Standard Model predictions. This enables us to put a lower bound on the selectron and the smuon masses.
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Submitted on : Friday, June 14, 2002 - 9:22:11 AM
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  • HAL Id : tel-00001412, version 1



Nabil Ghodbane. Recherche de sélectrons et de smuons dans l'expérience DELPHI au LEP. Physique des Hautes Energies - Expérience [hep-ex]. Université Claude Bernard - Lyon I, 2000. Français. ⟨tel-00001412⟩



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