Observation of a Near-ThresholdωJ/ψMass Enhancement in ExclusiveB→KωJ/ψDecays

We report the observation of a near-threshold enhancement in the $\omega J/\psi$ invariant mass distribution for exclusive $B\to K\omega J/\psi$ decays. The results are obtained from a $253{\mathrm{fb}}^{-1}$ data sample that contains $275\times {10}^6$ $B\overline{B}$ pairs that were collected near the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. The statistical significance of the $\omega J/\psi$ mass enhancement is estimated to be greater than $8\sigma$.