Search for B0 decays to invisible final states ( + γ ) at Belle

We report searches for B0 → invisible and B0 → invisible + γ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a 711 fb−1 data sample that contains 772 × 106 BB pairs and was collected near the Υ(4S) resonance with the Belle detector at the KEKB e+e− collider. We observe no significant signal for either decay and set upper limits on their branching fractions at 90% confidence level of B(B0 → invisible ) < 7.8 × 10−5 and B(B0 → invisible + γ ) < 1.6 × 10−5.