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Recherche de charginos et neutralinos dans le canal dimuon de même signe auprès de l'expérience D0-FNAL

Abstract : In the framework of the mSUGRA model which provides a simple breaking mecha-nism of supersymmetry, sparticles with masses beyond the kinematic reach of the LEPII experiments may be produced at the Tevatron $p\overline {p}$ collider at a center of masse energy of 1.96 TeV. A promising source of sparticles at the Tevatron collider is the associated production of the lightest chargino, $\tilde {chi}_1^± $, and the next to lightest neutralino, $\tilde {chi}_2^0$. Leptonic decay modes, $\tilde {chi}_2^0\to\tilde {chi}_1^0 $ l +l -and $\tilde {chi}_1^± \to\tilde {chi}_1^0 $ l±\nu_l, lead to a clean detector signature with three leptons and a large amount of missing transverse energy. In order to increase the sensitivity to signal in regions of mSUGRA parameters space leading to a very soft third lepton with small reconstruction efficiency, a selection based on two like sign leptons plus missing transverse energy has been developped. The particular signature with two like sign muons is presented in this dissertation. No evidence for supersymmetry has been observed in a dataset collected from april 2002 to February 2006 with the DØ detector at the Tevatron collider and corres-ponding to an integratedluminosity of 0.9f b−1. Then, limits on the product of the cross-section and the leptonic branching ratio, $\sigma (p\overline {p}\to\ tilde {chi}_1^± \tilde {chi}_2^0)$ ×BR(3ℓ), have been set as a function of the $\tilde {chi}_1^± $ mass. The results obtained with the like sign dimuon selection have been combined with the results of three trilepton selections. For mSUGRA models with enhanced leptonic decays, a $\tilde {chi}_1^± $ mass limit of 140 GeV/c2 has been derived at 95% confidence level.
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Submitted on : Friday, November 10, 2006 - 5:39:51 PM
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  • HAL Id : tel-00113149, version 1

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V. Lesne. Recherche de charginos et neutralinos dans le canal dimuon de même signe auprès de l'expérience D0-FNAL. Physique des Hautes Energies - Expérience [hep-ex]. Université Blaise Pascal - Clermont-Ferrand II, 2006. Français. ⟨tel-00113149⟩

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