Observation of and evidence for decays

Measurements of the branching fractions of $B_{s}^{0}\to {{K}^{*\pm }}{{K}^{\mp }}$ and $B_{s}^{0}\to {{K}^{*\pm }}{{\pi }^{\mp }}$ decays are performed using a data sample corresponding to $1.0\ {\rm f}{{{\rm b}}^{-1}}$ of proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of $7\;{\rm TeV}$ , where the ${{K}^{*\pm }}$ mesons are reconstructed in the $K_{S}^{0}{{\pi }^{\pm }}$ final state. The first observation of the $B_{s}^{0}\to {{K}^{*\pm }}{{K}^{\mp }}$ decay and the first evidence for the $B_{s}^{0}\to {{K}^{*-}}{{\pi }^{+}}$ decay are reported with branching fractions \begin{eqnarray*}\begin{array}{rcl} \bf{\mathcal{B}}\left( B_{s}^{0}\to {{K}^{*\pm }}{{K}^{\mp }} \right) & = & \left( 12.7\pm 1.9\pm 1.9 \right)\times {{10}^{-6}}, \\ \bf{\mathcal{B}}\left( B_{s}^{0}\to {{K}^{*-}}{{\pi }^{+}} \right) & = & \left( 3.3\pm 1.1\pm 0.5 \right)\times {{10}^{-6}}, \\ \end{array}\end{eqnarray*} where the first uncertainties are statistical and the second are systematic. In addition, an upper limit of $\mathcal{B}\left( {{B}^{0}}\to {{K}^{*\pm }}{{K}^{\mp }} \right)\lt 0.4\ (0.5)\times {{10}^{-6}}$ is set at $90\%\ (95\%)$ confidence level.