Production of J/ψ + ηc versus J/ψ plus J/ψ at the LHC: Importance of Real αs5 Corrections

We proceed for the first time to the evaluation of the Born cross section for J/psi + eta(c) production, namely, via g + g ! J/psi + eta(c) + g, and show that it has a harder P-T spectrum than the J/psi-pair yield at the Born level. If one stuck to a comparison at the Born level, one would conclude that J/psi + eta(c) production would surpass that of J/psi + J/psi at large P-T. This is nonetheless not the case since J/psi-pair production, as for single J/psi, receives leading-P-T contributions at higher orders in alpha(s). We also present the first evaluation of these leading-P-T next-to-leading order contributions. These are indeed significant for increasing P-T and are of essential relevance for comparison with forthcoming data. We also compute kinematic correlations relevant for double-parton-scattering studies. Finally, we evaluate the polarization of a J/psi accompanied by either an eta(c) or a J/psi and another light parton. These results may be of great help to understand the polarization of quarkonia produced at high energies.