Production of J/psi+eta(c) vs. J/psi+J/psi at the LHC: Impact of Real alpha_s^5 corrections

TL;DR

This paper evaluates the production cross sections and polarizations of J/psi+eta(c) and J/psi+J/psi at the LHC, highlighting the importance of higher-order alpha_s corrections for accurate predictions and comparison with experimental data.

Contribution

First calculation of the Born cross section for J/psi+eta(c) production and the first evaluation of leading-P_T NLO contributions, improving theoretical predictions for quarkonium production.

Findings

J/psi+eta(c) has a harder P_T spectrum at Born level.

Higher-order alpha_s corrections significantly increase cross sections at high P_T.

Results aid in understanding quarkonium polarization and double-parton scattering.

Abstract

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 Born level. If one stuck to a comparison at 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 polarisation of a J/psi accompanied either by a eta(c) or a J/psi and another light parton. These results may be of great help to understand the polarisation of quarkonia produced at high energies.