Oscillations of $B_s^0$ mesons as a probe of decays with invisible particles

A new experimental technique to study the decays of $B^0_s$ mesons into the final states involving unreconstructable particles is proposed. The method uses a characteristic feature of fast flavour oscillations of $B^0_s$ mesons. Analysis of the oscillation spectrum of partially reconstructed flavour-tagged $B^0_s$ decays provides information about the mass spectrum of invisible states in these decays and removes any background which does not come from the decays of $B^0_s$ mesons.