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Etude de la violation de CP dans le canal B0 -> J/Psi K0s et développement d'un compteur Tcherenkov à aerogel

Abstract : CP violation and the mass generation problem, will be the two fundamental points for Particle Physics at the dawn of the third millennium. The BaBar experiment, which is installed at PEP-II SLAC B-factory, aims to study CP violation in the B meson system. It will be then possible to test the standard model explanation of CP
violation and may be to highlight new sources.

In order to study CP violation with the BaBar experiment it is mandatory to identify most of the produced particles. The first part of this thesis presents the study we carried out on a project of Cherenkov aerogel threshold counters for pions kaons separation in the momentum region between 0.5 and 4.3 GeV/c. This study includes:
preliminary researches on materials (reflecting wrappings, wavelength shifters and aerogel), cells and light guides geometry and prototypes simulation. Test beams results have shown the feasibility of such a detector.

The second part of this thesis deals with the CP parameter measurement that could be achieved at the BaBar experiment for the B0 -> J/Psi K0s channel, where the J/Psi disintegrates in lepton mode. Are studied: the reconstruction efficiency, background level, tagging efficiency as well as the resolutions on the Bs vertexes
positions. The measurement of the expected asymmetry is made with a probabilistic method or a fit and the resolution on the parameter sin 2b that could be achieved is estimated. It is then shown that an uncertainty of 0.085 on sin 2b could be reached in 1 year of data taking at the BaBar experiment, corresponding to an integrated
luminosity of 30 fbarn-1.
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  • HAL Id : tel-00003058, version 1



Rémi Lafaye. Etude de la violation de CP dans le canal B0 -> J/Psi K0s et développement d'un compteur Tcherenkov à aerogel. Physique des Hautes Energies - Expérience [hep-ex]. Université de Savoie, 1998. Français. ⟨tel-00003058⟩



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