Type: Article
Publication Date: 2005-10-18
Citations: 6
DOI: https://doi.org/10.1103/physrevd.72.071102
We report the observation of the decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}}{K}^{\ensuremath{-}}$, where ${D}_{{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}}$ indicates a neutral $D$ meson detected in the final state ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$, excluding ${K}_{S}^{0}{\ensuremath{\pi}}^{0}$. This doubly Cabibbo-suppressed decay chain can be used to measure the CKM phase $\ensuremath{\gamma}$. Using about $229\ifmmode\times\else\texttimes\fi{}{10}^{6}$ ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}B\overline{B}$ events recorded by the BABAR experiment at the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ storage ring, we measure the branching fraction $\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}}{K}^{\ensuremath{-}})=(5.5\ifmmode\pm\else\textpm\fi{}1.0(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and the decay rate asymmetry $A({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}}{K}^{\ensuremath{-}})=\ensuremath{-}0.02\ifmmode\pm\else\textpm\fi{}0.16(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{syst}.)$ for the full decay chain.