Observation of the decay $B^{0} \to D^{0}K^{+}K^{-}$ with the LHCb detector at CERN

The first observation of the decay mode $B^{0} \to \bar{D}^{0} K^{+}K^{-}$ is presented using 0.62~fb$^{-1}$ of data collected by the LHCb detector in 2011. The branching fraction is measured with respect to the topologically similar decay mode, $B^{0} \to \bar{D}^{0} \pi^{+}\pi^{-}$. The ratio of branching fractions is measured to be \[\begin{array}{ccllllllll} \frac{{\cal B}\left(B^0 \to \bar{D}^0 K^+K^-\right)}{{\cal B}\left(B^0 \to \bar{D}^0 \pi^+\pi^-\right)} = 0.056 \pm 0.011 \pm 0.007, \\ \end{array} \] where the first uncertainty is statistical and the second is systematic. Using the world average value for the denominator yields \[\begin{array}{ccllllllll} {\cal B}\left(B^0 \to \bar{D}^0 K^+K^-\right) = (4.7 \pm 0.9 \pm 0.6 \pm 0.5)\times 10^{-5}, \\ \end{array} \] where the third uncertainty is from ${\cal B}\left(B^0 \to \bar{D}^0 \pi^+\pi^-\right)$. Secondly, evidence for the $B^{0}_{s} \to \bar{D}^{0} K^{+}K^{-}$ decay mode is presented. The branching fraction ratio with respect to $B^{0} \to \bar{D}^{0} K^{+}K^{-}$ is found to be \[\begin{array}{ccllllllll} \frac{{\cal B}\left(B^{0}_{s} \to \bar{D}^0 K^+K^-\right)}{{\cal B}\left(B^0 \to \bar{D}^0 K^+K^-\right)} = 0.90 \pm 0.27 \pm 0.20, \\ \end{array} \] where the first uncertainty is statistical and the second is systematic.