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Recherche du boson de Higgs du Modèle Standard dans le canal de désintégration ZH->nu nu bb sur le collisionneur Tevatron dans l'expérience D0. Développement d'une méthode d'étiquetage des jets de quark b avec des muons de basses impulsions transverses

Abstract : In the Standard Model of particle physics, the Higgs boson generates elementary particle masses. Current theoretical and experimental constraints lead to a Higgs boson mass between 114.4 and 158 GeV with 95% confidence level. Moreover, Tevatron has recently excluded the mass ranges between 100 and 109 GeV, 158 and 175 GeV with 95% confidence level. These results gives a clear indication to search for a Higgs boson at low mass. The DØ detector is located near Chicago, at the Tevatron, a proton-antiproton collider with an energy in the center of mass of 1.96 TeV. The topic of this thesis is the search for a Higgs boson in association with a Z boson. This channel is sensitive to low mass Higgs boson (<135 GeV) which has a branching ratio H->bb close to 80% in this mass range. The decay channel ZH->nu nu bb studied has in the final state 2 heavy-flavor jets and some missing transverse energy due to escaping neutrinos. The heavy-flavor jets identification ("b-tagging") is done with a new algorithm (SLTNN) developped specifically for semi-leptonic decay of b quarks. The Higgs boson search analysis was performed with 3 fb-1 of data. The use of SLTNN increases by 10% the Higgs boson signal efficiency. The global analysis sensitivity improvement, however, is rather low (<1%) after taking into account the backgrounds and systematic uncertainties.
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https://tel.archives-ouvertes.fr/tel-00557839
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Submitted on : Thursday, January 20, 2011 - 11:08:59 AM
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D. Jamin. Recherche du boson de Higgs du Modèle Standard dans le canal de désintégration ZH->nu nu bb sur le collisionneur Tevatron dans l'expérience D0. Développement d'une méthode d'étiquetage des jets de quark b avec des muons de basses impulsions transverses. Physique des Hautes Energies - Expérience [hep-ex]. Université de la Méditerranée - Aix-Marseille II, 2010. Français. ⟨tel-00557839⟩

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