Observation of the decay $B^0\to {\eta }^{\prime }{K}^{\ast }(892{)}^0$

Abstract

We report a search for charmless hadronic decays of neutral $B$ mesons to ${\eta }^{\prime }{K}^{\ast }(892{)}^0$. The results are based on a 711fb${}^{-1}$ data sample that contains $772\times 10^{6}B\overline{B}$ pairs, collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction $\mathcal{B}[B^0\to {\eta }^{\prime }{K}^{\ast }(892{)}^0]=[2.6\pm 0.7(\mathrm{stat})\pm 0.2(\mathrm{syst})]\times 10^{-6}$. We also measure the $CP$ violating asymmetry as ${\mathcal{A}}_{CP}[B^0\to {\eta }^{\prime }{K}^{\ast }(892{)}^0]=-0.22\pm 0.29(\mathrm{stat})\pm 0.07\mathrm{syst}$.

11 pages, 2 figures, submitted PRD(RC)