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Etude de la production de charme dans les désintégrations des mésons beaux avec l'expérience BABAR

Abstract : The BABAR experiment, located at SLAC (Stanford, California), has been dedicated, since 1999, to the study of $B$ meson decays produced in electron positron collisions with an energy in the center of mass frame equal to the mass of $\Upsilon(4S)$ resonance. In this experiment, the charged particles identification is provided, in particular by the measurement of the energy loss per unit length in the drift chamber. In order to improve the calibration of this quantity, a selection of electrons/positrons from radiative Bhabha events was performed; with the new sample the charge asymmetry in the charged particles reconstruction was reduced. In $B$ meson decays, the inclusive production of charmed particles ($D^0$, $\overline(D)^0$, $D^(\pm)$ , $D_s^(pm)$, $\Lambda_c^(\pm)$) is measured with a new analysis method, made possible by the large statistics accumulated by the BABAR experiment. $B$ and $\overline(B)$ mesons are produced simultaneously from the $\Upsilon(4S)$ resonance. The events are selected by reconstructing completely one $B$ in a hadronic channel. Charmed particles from the other $B$ are then reconstructed with the remaining tracks. This enables the measurement of the total number of charm produced in $B^+$ and in $B^0$ decays separating the correlated charm production (quark transitions: $b\rightarrow c X$) from the anti-correlated production (quark transitions: $b\rightarrow \overline(c) X$). The results obtained on an integrated luminosity of $210~fb^(-1)$ are the following~: \begin(displaymath) \begin(array)(l@(=\ ) c @(\hspace(1.5 cm)) l @(=\ ) c r ) N_(c)^(B^+) & 0.970 \pm 0.042 & N_(\overline(c))^(B^+) & 0.262\pm0.034 & \\ N_(c)^(B^0) & 0.950 \pm 0.057 & N_(\overline(c))^(B^0) & 0.285\pm0.048 &. \\ \end(array) \end(displaymath) This new method also allows the measurement of the momentum of the charmed particles in the $B$ rest frame. Access to the different production mechanisms of these particles is thereby provided.
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Submitted on : Wednesday, July 6, 2005 - 9:57:19 AM
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  • HAL Id : tel-00009690, version 1

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Fabrice Couderc. Etude de la production de charme dans les désintégrations des mésons beaux avec l'expérience BABAR. Physique des Hautes Energies - Expérience [hep-ex]. Université de Savoie, 2005. Français. ⟨tel-00009690⟩

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