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Étude de la violation de symétrie CP à l'aide du canal de désintégration B0->rho0rho0 dans l'expérience BaBar

Abstract : The measurement of the CP violating parameters in the b->uubard decays allow in principle to determine sin(2alpha), where alpha is one of the angle of the unitarity triangle. However, due to the presence of loop diagrams, the so-called penguin diagrams, the experimental measurement only gives information about an effective quantity of \alpha : æff. The measurements in the B->rho0rho0 decay allow to perform for the first time a full isospin analysis in the B->rhorho modes and hence to determine in principle the shift \alpha-æff induced by the penguin diagramms. The B->rho0rho0 decay was studied with the final \babar sample containing $465 10^6$ $\Y4S\to\BB$ events collected at the PEP-II collisionner. The B->rho0rho0 branching ratio BR=0.92±0.32\±0.14 10^{-6} and the longitudinal polarization fraction fL=0.75^{+0.11}_{-0.14}±0.03 were measured. The evidence for the B->rho0rho0 signal has a significance of 3,1 \sigma including systematical uncertainties. The proper-time dependence of the longitudinal component in the decay was studied and the CP-violating coefficients S^{00}_L = 0.3\pm0.7\pm0.2, C^{00}_L = 0.2\pm0.8\pm0.2. The implication of these results on the unitarity triangle alpha was studied by performing an isospin analysis. Using the BABAR results for the B->rho+rho- and B±->rho±pi0, the 68% (90%) confidence interval on the shift in alpha induced by the penguin diagrams is |\alpha-æff|<15.6° (<17.6°).
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Contributor : Loïc Estève <>
Submitted on : Tuesday, January 5, 2010 - 6:38:56 PM
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  • HAL Id : tel-00444148, version 1


Loïc Estève. Étude de la violation de symétrie CP à l'aide du canal de désintégration B0->rho0rho0 dans l'expérience BaBar. Physique des Hautes Energies - Expérience [hep-ex]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00444148⟩



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