Observation of $\overline{B} \to D^{(*)} \pi^+\pi^- \ell^-\overline{\nu}$ decays in $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance

J. P. Lees 1 V. Poireau 1 V. Tisserand 1 N. Arnaud 2 M. Davier 2 D. Derkach 2 G. Grosdidier 2 F. Le Diberder 2 A. M. Lutz 2 B. Malaescu 2 P. Roudeau 2 A. Stocchi 2 G. Wormser 2
1 LAPP/Laboratoire d'Annecy-le-Vieux de Physique des Particules - Laboratoire d'Annecy de Physique des Particules
2 LAL - Laboratoire de l'Accélérateur Linéaire
Abstract : We report on measurements of the decays of $\overline{B}$ mesons into the semileptonic final states $\overline{B} \to D^{(*)} \pi^+\pi^- \ell^-\overline{\nu}$, where $D^{(*)}$ represents a $D$ or $D^*$ meson and $\ell^-$ is an electron or a muon. These measurements are based on $471\times 10^6$ $B\overline{B}$ pairs recorded with the $BABAR$ detector at the SLAC asymmetric $B$ Factory PEP-II. We determine the branching fraction ratios $R^{(*)}_{\pi^+\pi^-} = \mathcal{B}(\overline{B} \to D^{(*)} \pi^+\pi^- \ell^- \overline{\nu})/\mathcal{B}(\overline{B} \to D^{(*)} \ell^-\overline{\nu})$ using events in which the second $B$ meson is fully reconstructed. We find $R_{\pi^+\pi^-} = 0.067 \pm 0.010 \pm 0.008$ and $R^*_{\pi^+\pi^-} = 0.019 \pm 0.005 \pm 0.004$, where the first uncertainty is statistical and the second is systematic. Based on these results, we estimate that $\overline{B} \to D^{(*)}\pi\pi\ell^-\overline{\nu}$ decays, where $\pi$ denotes both a $\pi^\pm$ and $\pi^0$ meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.
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Contributor : Sabine Starita <>
Submitted on : Friday, July 31, 2015 - 10:14:57 AM
Last modification on : Thursday, January 11, 2018 - 6:14:21 AM

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J. P. Lees, V. Poireau, V. Tisserand, N. Arnaud, M. Davier, et al.. Observation of $\overline{B} \to D^{(*)} \pi^+\pi^- \ell^-\overline{\nu}$ decays in $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance. Physical Review Letters, American Physical Society, 2016, 116, pp.041801. ⟨10.1103/PhysRevLett.116.041801⟩. ⟨in2p3-01182326⟩

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