Heavy quarkonium production in double pomeron exchange processes in perturbative QCD

We calculate the heavy quarkonium production in double pomeron exchange processes in perturbative QCD by using two-gluon exchange model. For the P-wave χJ productions, we find χ1 and χ2 production amplitudes which vanish in the forward scattering limit. We also calculate direct J/ψ(ϒ)+γ production in the same approach, and these direct contributions are much smaller than the feeddown contributions from the P-wave states.