Search for Invisible Decay of the $\Upsilon(1S)$
  We report results of a search for the invisible decay of the Upsilon(1S) via the Upsilon(3S)->pi+pi-Upsilon(1S) transition using a data sample of 2.9 fb^{-1} at the Upsilon(3S) resonance. The data were collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. No signal is found, and an upper limit for the branching fraction at the 90% confidence level is determined to be B(Upsilon(1S)->invisible) < 2.5x10^{-3}. 
The Belle Collaboration: O. Tajima, H. Hayashii, M. Hazumi, K. Inami,   Y. Iwasaki, S. Uehara, et al