# Observation of the Decay B^{-} \rightarrow D_{s}^{(*)+} K^{-} \ell^{-} \bar{\nu}_{\ell}

Abstract : We report the observation of the decay $B^{-} \rightarrow D^{(*)+}_{s} K^{-} \ell^{-} \bar{\nu}_{\ell}$ based on $342 \mathrm {\,fb}^{-1}}$ of data collected at the $\Y4S$ resonance with the BABAR detector at the PEP-II $e^{+}e^{-}$ storage rings at SLAC. A simultaneous fit to three $D^{+}_{s}$ decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay $B^{-} \rightarrow D^{(*)+}_{s} K^{-} \ell^{-} \bar{\nu}_{\ell}$ with a significance greater than five standard deviations (including systematic uncertainties) and measure its branching fraction to be $\BR(B^{-} \rightarrow D^{(*)+}_{s} K^{-} \ell^{-} \bar{\nu}_{\ell}) = [6.13^{+1.04}_{-1.03}(\mathrm{stat.})\pm0.43(\mathrm{syst.}) \pm 0.51(\BR(D_{s}))]\times10^{-4}$, where the last error reflects the limited knowledge of the $D_{s}$ branching fractions.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00556686
Contributor : Claudine Bombar <>
Submitted on : Monday, January 17, 2011 - 3:37:56 PM
Last modification on : Wednesday, July 22, 2020 - 9:54:17 AM

### Citation

P. del Amo Sanchez, J.P. Lees, V. Poireau, E. Prencipe, V. Tisserand, et al.. Observation of the Decay B^{-} \rightarrow D_{s}^{(*)+} K^{-} \ell^{-} \bar{\nu}_{\ell}. Physical Review Letters, American Physical Society, 2011, 107, pp.041804. ⟨10.1103/PhysRevLett.107.041804⟩. ⟨in2p3-00556686⟩

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