Observation of Ds+K− and Evidence for Ds+π− Final States in Neutral B Decays

Le résumé fourni par la source

We report the first observation of a $B$ meson decay that is not accessible by a direct spectator process. The channel ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{K}^{\ensuremath{-}}$ is found in a sample of $85\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events, collected with the Belle detector at KEKB, with a branching fraction $\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{K}^{\ensuremath{-}})=({4.6}_{\ensuremath{-}1.1}^{+1.2}\ifmmode\pm\else\textpm\fi{}1.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. We also obtain evidence for the ${B}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay with branching fraction $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})=({2.4}_{\ensuremath{-}0.8}^{+1.0}\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. This value may be used to extract a model-dependent value of $|{V}_{ub}|$.

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