Violation de CP dans le système $B^0−\bar{B}^0$ avec le détecteur CMS à LHC et étude des chambres gazeuses à micropistes

Abstract : This thesis has been performed for the CMS project at the LHC, the proton-proton collider at CERN, whose first data taking is foreseen for the years 2004-2005. This work is divided in two parts. The first part includes a general study about low energy electron identification using the very fine granularity and the high resolution of the electromagnetic calorimeter of CMS. The efficiency of this algorithm is estimated to be about 60% and the hadron rejection factor is $\sim$400. These identified electrons can be used for the B hadron tagging as well as for the reconstruction of the semi-inclusive decay $B^0_d -> J/\Psi(->e+e-) +X$. The new sensitivities of the CMS detector to the angles $\alpha$ and $\beta$ of the CKM unitarity triangle with this new possibilities and new proton structure functions are: $\delta$(sin 2$\alpha$) = 0.06$^{+0.018}_{-0.014} $ $\delta$(sin 2$\beta$) = 0.053$^{+0.017}_{-0.012}$ This results are comparable to what is expected for the dedicated B-Physics experiments. The second part concerns the development of a new type of microstrip gas chambers (MGC) where the anodes are separated from the cathode plane by a few microns. This geometry allows a fast charge collection $\sim$10ns), gain values of more than 3000 and an energy resolution of 20 % for the peek of a 55Fe source.
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Theses
Physique des Hautes Énergies - Expérience [hep-ex]. Université Louis Pasteur - Strasbourg I, 1997. Français


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Pascal Pralavorio. Violation de CP dans le système $B^0−\bar{B}^0$ avec le détecteur CMS à LHC et étude des chambres gazeuses à micropistes. Physique des Hautes Énergies - Expérience [hep-ex]. Université Louis Pasteur - Strasbourg I, 1997. Français. <tel-00393905>

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