Central exclusive production of the scalar χc meson at the Fermilab Tevatron, BNL RHIC, and CERN LHC energies

We calculate several differential distributions for exclusive double-diffractive χc(0++) production in the proton-antiproton collisions at the Tevatron and in proton-proton collisions at RHIC and LHC. We use unintegrated gluon distributions (UGDFs) within the kt-factorization approach. The g*g*→χc(0++) transition vertex is calculated as a function of gluon virtualities via the standard perturbative nonrelativistic QCD technique. The off shell effects are discussed and quantified. They lead to a reduction of the cross section by a factor of 2-5, depending on the position in the phase space and UGDFs. Different models of UGDFs are used and the results are shown and discussed. The cross section for the diffractive component depends strongly on UGDFs. Transverse momentum distribution of χc(0) shows a well localized minimum. We calculate also the differential distributions for the γ*γ*→χc(0++) fusion mechanism. The integrated cross section for photon-photon fusion is much smaller than that of diffractive origin. The two components have very different dependence on the momentum transfers t1, t2 in the nucleon lines as well as azimuthal-angle correlations between both outgoing nucleons.