The first observation of the $B_s^0\to {\overline{D}}^0{K}^{+}{K}^{-}$ decay is reported, together with the most precise branching fraction measurement of the mode $B^0\to {\overline{D}}^0{K}^{+}{K}^{-}$. The results are obtained from an analysis of $pp$ collision data corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$. The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction of the $B^0\to {\overline{D}}^0{K}^{+}{K}^{-}$ decay is measured relative to that of the decay $B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}$ to be $\frac{\mathcal{B}(B^0\to {\overline{D}}^0{K}^{+}{K}^{-})}{\mathcal{B}(B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-})}=(6.9\pm 0.4\pm 0.3)\%$, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the $B_s^0\to {\overline{D}}^0{K}^{+}{K}^{-}$ decay mode relative to that of the corresponding $B^0$ decay is $\frac{\mathcal{B}(B_s^0\to {\overline{D}}^0{K}^{+}{K}^{-})}{\mathcal{B}(B^0\to {\overline{D}}^0{K}^{+}{K}^{-})}=(93.0\pm 8.9\pm 6.9)\%$. Using the known branching fraction of $B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}$, the values of $\mathcal{B}(B^0\to {\overline{D}}^0{K}^{+}{K}^{-})=(6.1\pm 0.4\pm 0.3\pm 0.3)\times {10}^{-5}$ and $\mathcal{B}(B_s^0\to {\overline{D}}^0{K}^{+}{K}^{-})=(5.7\pm 0.5\pm 0.4\pm 0.5)\times {10}^{-5}$ are obtained, where the third uncertainties arise from the branching fraction of the decay modes $B^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}$ and $B^0\to {\overline{D}}^0{K}^{+}{K}^{-}$, respectively.

• Received 6 July 2018

DOI:https://doi.org/10.1103/PhysRevD.98.072006

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© 2018 CERN, for the LHCb Collaboration