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Mesure des électrons et recherche de bosons de Higgs en canaux multi-leptons avec l'expérience CMS au LHC

Abstract : This thesis presents three years of work with the CMS experiment, in the context of the first LHC collisions. Electron objects were studied in particular, as major tools for multi-lepton analyses, in particular the H → ZZ(∗) → 4ℓ analysis. During the first months of collisions, we took part in the validation of data registered by the electromagnetic calorimeter. We also measured the efficiency of the level-1 electron and photon trigger during the whole 2010 year. The plateau efficiency is of 99.6 % (resp. 98.5 %) on electrons in the barrel part (resp. in the endcap part) of the calorimeter. In order to optimize the discovery potential, we built a new electron charge measurement algorithm. In CMS, this measurement is affected by the large amount of material present in the inner tracker. The performance of this algorithm was measured on 2010 data, for electrons from Z boson decay passing a standard selection. The probability of charge mis-identification is of 1.06 % (0.19 % with a specific selection), in agreement with the simulation. The physics analysis that was built during this PhD searches doubly charged Higgs bosons decaying into lepton pairs. For the amount of data registered in 2010, one background event is expected to pass the selection, while the amount of signal events depends on the mass hypothesis and on the model. One event was found on data, in agreement with the background expectation, hence the signal was excluded on larger mass ranges than previous experiments: a mass limit was set between 122 GeV and 176 GeV, depending on the model.
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Contributor : Clémentine Broutin Connect in order to contact the contributor
Submitted on : Monday, August 29, 2011 - 1:37:48 PM
Last modification on : Wednesday, March 27, 2019 - 4:40:12 PM
Long-term archiving on: : Sunday, December 4, 2016 - 2:09:32 PM


  • HAL Id : pastel-00617514, version 1



Clémentine Broutin. Mesure des électrons et recherche de bosons de Higgs en canaux multi-leptons avec l'expérience CMS au LHC. Physique des Hautes Energies - Expérience [hep-ex]. Ecole Polytechnique X, 2011. Français. ⟨NNT : 1695001552S⟩. ⟨pastel-00617514⟩



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