First observation of the decay $B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0}$

Abstract

The first observation of the decay $B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0}$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb${}^{-1}$ of $pp$ collisions at $\sqrt{s}=7TeV$, collected with the LHCb detector. A yield of $30\pm 6$ $B_s^0\to (K^{+}{K}^{-})(K^{-}\ddot{I}{€}^{+})$ decays is found in the mass windows $1012.5<M(K^{+}{K}^{-})<1026.5MeV/c^2$ and $746<M(K^{-}\ddot{I}{€}^{+})<1046MeV/c^2$. The signal yield is found to be dominated by $B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0}$ decays, and the corresponding branching fraction is measured to be $\mathcal{B}(B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0})=(1.10\pm 0.24(stat)\pm 0.14(syst)\pm 0.08(f_d/f_s))\times 10^{-6}$, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions $f_d/f_s$ which accounts for the different production rate of $B^0$ and $B_s^0$ mesons. The significance of $B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0}$ signal is 6.1 standard deviations. The fraction of longitudinal polarization in $B_s^0\to \ddot{I}•{\bar{K}}^{\ast 0}$ decays is found to be $f_0=0.51\pm 0.15(stat)\pm 0.07(syst)$.