Observation of the Decay B−→Ds(*)+K−ℓ−ν¯ℓ

Le résumé fourni par la source

We report the observation of the decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{s}^{(*)+}{K}^{\ensuremath{-}}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ based on $342\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector at the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ 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 ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{s}^{(*)+}{K}^{\ensuremath{-}}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be $\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{s}^{(*)+}{K}^{\ensuremath{-}}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=[{6.13}_{\ensuremath{-}1.03}^{+1.04}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.43(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.51\mathbf{(}\mathcal{B}({D}_{s})\mathbf{)}]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the last error reflects the limited knowledge of the ${D}_{s}$ branching fractions.

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