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Mesure des rapports d'embranchement et recherche de la violation de CP dans les modes B0->rho pi, rho K

Abstract : The BABAR experiment, at the PEP-II collider at SLAC, has been studying since 1999 CP violation in the B meson system. After the precise measurement of sin2beta one is now concentrating on measuring the angles alpha and gamma of the unitarity triangle. The work presented in this thesis concerns the measurement of the angle alpha in the B0->rhopi mode. We realized a CP time-dependant analysis, as well of the branching ratio measurements of the B0->rho+-pi-+ and B0->rho-K+ modes. The results obtained on an integrated luminosity of 80.9 fb-1 are the following: B(B0->rho+-pi-+) = (22.6 +- 1.8 +- 2.2) 10-6, B(B0->rho-K+) = ( 7.3 +- 1.3 +- 1.3) 10-6, ACP(rhopi) = -0.18 +- 0.08 +- 0.03, ACP(rhoK) = -0.28 +- 0.17 +- 0.08, C(rhopi) = -0.36 +- 0.18 +- 0.04, S(rhopi) = -0.19 +- 0.24 +- 0.03, delatC(rhopi) = 0.28 +- 0.19 +- 0.04, deltaS(rhopi) = 0.15 +- 0.25 +- 0.03. We also measured the branching ratio of B0->rho0pi0 with a significance of 2.7 sigmas. We therefore put the following upper limit at 90 % CL: B(B0->rho0pi0) < 2.7 x 10-6 at 90 % CL. Finally, we built the heart of a complete Dalitz plot analysis of B0->pi+pi-pi0, and estimated the experimental sensibility on alpha. The results obtained on the B0->rhopi modes are interpreted in terms of constraints on the angle alpha within methods using SU(2) and SU(3) symmetries. We also measured the branching ratio of B0->a0pi using a reduced luminosity, leading to the result: B(B0->a0pi) = (6.2 +3.0-2.5 +- 1.1) 10-6. Some phenomenological studies have been performed to infer the feasibility of a CP analysis to determine the angle alpha thanks to this mode. Finally, we describe the improvements made on the SVT radiation protection system for the injection periods. Outside the BABAR collaboration scope, we developed a package called CKMFitter allowing us to perform a global analysis of the CKM matrix, within a frequentist statistical approach.
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Submitted on : Thursday, July 31, 2003 - 2:59:45 PM
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  • HAL Id : tel-00003224, version 1

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Sandrine Laplace. Mesure des rapports d'embranchement et recherche de la violation de CP dans les modes B0->rho pi, rho K. Physique des Hautes Energies - Expérience [hep-ex]. Université Paris-Diderot - Paris VII, 2003. Français. ⟨tel-00003224⟩

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