Improved Measurements of $\bar{B}^0 \to D^0 \bar{K}^0$ and $\bar{B}^0 \to D^0 \bar{K}^{*0}$ Branching Fractions

Abstract

We report on an improved study of $\bar{B}^0 \to D^{(*)0} \bar{K}^{(*)0}$ decays, based on $274 \times 10^6$ $B{\bar B}$ events collected with the Belle detector at KEKB. The following branching fractions have been measured: ${\cal B}(\bar{B}^0 \to D^0 \bar{K}^0) = (3.72 \pm 0.65 \pm 0.37) \times 10^{-5}$ and ${\cal B}(\bar{B}^0 \to D^0 \bar{K}^{*0}) = (3.08 \pm 0.56 \pm 0.31) \times 10^{-5}$. We also obtain evidence with $3.2σ$ significance for $\bar{B}^0 \to D^{*0} \bar{K}^0$ with ${\cal B}(\bar{B}^0 \to D^{*0} \bar{K}^0) = (3.2^{+1.2}_{-1.1} \pm 0.4) \times 10^{-5}$. No significant signal has been found for the $\bar{B}^0 \to D^{*0} \bar{K}^{*0}$ and $\bar{B}^0 \to \bar{D}^{(*)0} \bar{K}^{*0}$ decay modes, and upper limits at 90% CL are presented.