Measurement of the Branching Fractions and $CP$ Asymmetry of $B^{-}\to D_{(CP)}^0{K}^{-}$ Decays with the BABAR Detector

We present a study of $B^{-}\to D_{CP}^0{K}^{-}$ decays, where $D_{CP}^0$ is reconstructed in $CP$-even channels, based on a sample of $88.8\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage ring. We measure the ratio of Cabibbo-suppressed to Cabibbo-favored branching fractions $\mathcal{B}(B^{-}\to D_{CP}^0{K}^{-})/\mathcal{B}(B^{-}\to D_{CP}^0{\pi }^{-})=[8.8\pm 1.6(\mathrm{stat})\pm 0.5(\mathrm{syst})]\times {10}^{-2}$ and the $CP$ asymmetry $A_{CP}=0.07\pm 0.17(\mathrm{stat})\pm 0.06(\mathrm{syst})$. We also measure $\mathcal{B}(B^{-}\to D^0{K}^{-})/\mathcal{B}(B^{-}\to D^0{\pi }^{-})=[8.31\pm 0.35(\mathrm{stat})\pm 0.20(\mathrm{syst})]\times {10}^{-2}$ using a sample of $61.0\times {10}^6$ $B\overline{B}$ pairs.

Figure 1

Distributions of $\Delta E$ for events enhanced in $B\to D^{0}K$ signal. Top: $D^0\to K^{-}{\pi }^{+}$, $K^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$, $K^{-}{\pi }^{+}{\pi }^0$; bottom: $D^0\to K^{-}{K}^{+}$, ${\pi }^{-}{\pi }^{+}$. Solid curves represent projections of the maximum likelihood fit; dashed, dashed-dotted, and dotted curves represent, respectively, the $B\to D^{0}K$, $B\to D^0\pi$, and background contributions.