Search for B -> K-(*()) v(v)over-bar and invisible quarkonium decays

We search for the flavor-changing neutral-current decays B→K(*)ννbar, and the invisible decays J/ψ→ννbar and ψ(2S)→ννbar via B→K(*)J/ψ and B→K(*)ψ(2S), respectively, using a data sample of 471×10^6 BBbar pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Υ(4S)→BBbar decay, and search for the B→K(*)ννbar 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+ννbar)<3.7×10−5, ℬ(B0→K0ννbar)<8.1×10−5, ℬ(B+→K*+ννbar)<11.6×10−5, ℬ(B0→K*0ννbar)<9.3×10−5, and combined upper limits of ℬ(B→Kννbar)<3.2×10−5 and ℬ(B→K∗ννbar)<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→ννbar)<3.9×10−3 and ℬ(ψ(2S)→ννbar)<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(*)ννbar decays over the full kinematic spectrum.