Search for $B^{0}$ decays to invisible final states at Belle
  We report a search for $B^{0}$ decays into invisible final states using a data sample of $657 \times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The signal is identified by fully reconstructing a hadronic decay of the accompanying $B$ meson and requiring no other particles in the event. No significant signal is observed, and we obtain an upper limit of $1.3 \times 10^{-4}$ at the 90% confidence level for the branching fraction of invisible $B^{0}$ decay. 
Belle Collaboration: C.-L. Hsu, P. Chang, I. Adachi, H. Aihara, K.   Arinstein, D. M. Asner, V. Aulchenko, T. Aushev, A. M. ...
hep-ex