Search for double charmonium decays of the P-wave spin-triplet bottomonium states

Using a sample of 158×106 Υ(2S) events collected with the Belle detector, we search for the first time for double-charmonium decays of the P-wave spin-triplet bottomonium states (Υ(2S) →γχ _bJ, χ _bJ→J/ψJ/ψ, J/ψψ ^′, ψ ^′ψ ^′ for J=0, 1, and 2). No significant χ _bJ signal is observed in the double-charmonium mass spectra, and we obtain the following upper limits: B(χ _bJ→J/ψJ/ψ)<7.1×10 ^-5, 2.7×10 ^-5, 4.5×10 ^-5, B(χ _bJ→ J/ψψ ^′)<1.2×10 ^-4, 1.7×10 ^-5, 4.9×10 ^-5, B(χ _bJ→ψ ^′ψ ^′)<3. 1×10 ^-5, 6.2×10 ^-5, 1.6×10 ^-5 for J=0, 1, and 2, respectively, at the 90% confidence level. These limits are significantly lower than the central values (with uncertainties of 50% to 70%) predicted using the light cone formalism but are consistent with calculations using the nonrelativistic QCD (NRQCD) factorization approach.