Search for B→K^{(*)}νν[over ¯] and invisible quarkonium decays

We search for the flavor-changing neutral-current decays B→K(*)νν¯, and the invisible decays J/ψ→νν¯ and ψ(2S)→νν¯ via B→K(*)J/ψ and B→K(*)ψ(2S), respectively, using a data sample of 471×106 BB¯¯¯ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Υ(4S)→BB¯¯¯ decay, and search for the B→K(*)νν¯ 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+νν¯)<3.7×10−5, B(B0→K0νν¯)<8.1×10−5, B(B+→K*+νν¯)<11.6×10−5, B(B0→K*0νν¯)<9.3×10−5, and combined upper limits of B(B→Kνν¯)<3.2×10−5 and B(B→K∗νν¯)<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→νν¯)<3.9×10−3 and B(ψ(2S)→νν¯)<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(*)νν¯ decays over the full kinematic spectrum.