Search for B→K(*) vv̄ and invisible quarkonium decays

We search for the flavor-changing neutral-current decays B→K(*) νν̄, and the invisible decays J/ψ→νν̄ and ψ(2S)→νν̄ via B→K(*) J/ψ and B→K(*) ψ(2S), respectively, using a data sample of 471×106 BB̄ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Υ(4S)→BB̄ decay, and search for the B→K(*) νν̄ decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of B(B⁺→K ⁺νν̄)<3.7×10^-5, B(B0→K0νν ̄)<8.1×10^-5, B(B⁺→K ^*+νν̄)<11.6×10^-5, B(B0→K^*0νν̄)<9.3×10^-5, and combined upper limits of B(B→Kνν̄)<3.2×10^-5 and B(B→K^*νν̄)<7.9×10^-5, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of B(J/ψ→νν̄)<3. 9×10^-3 and B(ψ(2S)→νν̄)<15. 5×10^-3 at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the B→K(* νν̄ decays over the full kinematic spectrum.