Nonperturbative and spin effects in the central exclusive production of the tensor χc(2+) meson

Summary, in English

We discuss central exclusive production (CEP) of the tensor χc(2 ⁺) meson in proton-(anti)proton collisions at Tevatron, RHIC, and LHC energies. The amplitude for the process is derived within the kt-factorization approach. Differential and total cross sections are calculated for several unintegrated gluon distribution functions (UGDFs). We compare exclusive production of all charmonium states χc(0⁺), χc(1⁺) and χc(2⁺). Good description of the recent Tevatron data is achieved both with Martin-Ryskin phenomenological UGDF and UGDF based on unified BFKL-DGLAP approach. Unlike for Higgs production, the main contribution to the diffractive amplitude of heavy quarkonia comes from nonperturbative region of gluon transverse momenta Q +,2⁺) to the J/Ψ+γ channel to be comparable or larger than that of the χc(0⁺) one. This is partially due to a significant contribution from lower polarization states λ=0 for χc(1⁺) and λ=0, ±1 for χc(2⁺) meson. Corresponding theoretical uncertainties are discussed.