Measurements ofBDecays to Two Kaons

We report measurements of $B$ meson decays to two kaons using $253{\mathrm{fb}}^{-1}$ of data collected with the Belle detector at the KEKB energy-asymmetric $e^{+}{e}^{-}$ collider. We find evidence for signals in $B^{+}\to {\overline{K}}^0{K}^{+}$ and $B^0\to K^0{\overline{K}}^0$ with significances of $3.0\sigma$ and $3.5\sigma$, respectively. (Charge-conjugate modes are included.) The corresponding branching fractions are measured to be $\mathcal{B}(B^{+}\to {\overline{K}}^0{K}^{+})=(1.0\pm 0.4\pm 0.1)\times {10}^{-6}$ and $\mathcal{B}(B^0\to K^0{\overline{K}}^0)=(0.8\pm 0.3\pm 0.1)\times {10}^{-6}$. These decay modes are examples of hadronic $b\to d$ transitions. No signal is observed in the decay $B^0\to K^{+}{K}^{-}$, and we set an upper limit of $3.7\times {10}^{-7}$ at 90% confidence level.