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Recherche du boson de Higgs standard dans le canal WH à l'expérience D0 auprès du Tevatron

Abstract : The Higgs mechanism provides the Standard Model with an appropriate theory of the origin of the mass of gauge bosons and elementary fermions. The Higgs boson has not yet been discovered, but a lower limit on its mass has been set at 114.4 GeV at 95% confidence level by the Lep collaborations. Higgs searches are now being pursued at the Tevatron, a proton - anti-proton collider with a centre-of- mass energy of 1.96TeV. At low mass the most sensitive channel is the associated production of a Higgs with a W boson. An analysis has been performed in the decay channel in which the Higgs goes into a bb pair and the W decays to a muon and a neutrino with 1 fb-1 of Run IIa data recorded by the DØ detector. The analysis relies on all the sub-detector components but most particularly on the calorimeter which is essential for reconstruction of the bb system. Good tracking and a b-identification neural network tool provide improved b-tagging performance which is crucial for this analysis. Because the energy resolution of jets is of paramount importance when hunting for a two-jet resonance bump, work has also been conducted on devising a better-performing calibration for jets which exhibit a muon and a neutrino in their fragmentation chain. The WH analysis is performed on a W+2 and W+3 jet event topology. Events containing a muon, missing transverse energy and two or three jets are selected; the jets are then b-tagged. The double-tagged and single-tagged channels are analysed separately so as to provide additional sensitivity. Signal-background separation via a neural network algorithm has furthermore been developed in the analysis in order to enhance sensitivity. This search for a standard Higgs boson has been conducted for Higgs masses ranging from 100GeV to 150GeV. Upper limits on production cross-section times branching ratio have been set. For a Higgs mass of 115GeV, the upper limit is set at 2.00 pb at 95% confidence level in the channel WH to munubb and 1.37 pb when combining the two channels WH to munubb and WH to enubb, which is to be compared to the theoretical prediction of 0.136 pb. Those results have been submitted for publication, and are used in the global combination of Cdf's and DØ's Higgs analyses.
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Contributor : Lellouch Jeremie <>
Submitted on : Tuesday, October 14, 2008 - 11:15:01 AM
Last modification on : Friday, May 29, 2020 - 3:57:05 PM
Long-term archiving on: : Monday, June 7, 2010 - 6:07:42 PM

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  • HAL Id : tel-00330359, version 1

Citation

Jeremie Lellouch. Recherche du boson de Higgs standard dans le canal WH à l'expérience D0 auprès du Tevatron. Physique des Hautes Energies - Expérience [hep-ex]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00330359⟩

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