Production of quarkonium pairs in high-energy proton-proton collisions

Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland

^* e-mail: wolfgang.schafer@ifj.edu.pl

Published online: 1 February 2019

Abstract

Recently there has been much interest in the pair production of quarkonia (charmonia, bottomonia). There are two main motivations behind these studies: first, these processes may help to differentiate between different proposed production mechanisms via color-octet and color-singlet QQ̄ -pair production. Second, the production of quarkonium pairs is expected to receive an important contribution from double parton scattering (DPS) processes. There remain a number of open problems, especially with the CMS and ATLAS data. In the kinematics of these experiments, the leading order of $O\left({\alpha }_S^4\right)$ is clearly not sufficient. The double parton scattering (DPS) contribution was claimed to be large or even dominant in some corners of the phase space, when the rapidity distance Δy between two J/ψ mesons is large. However the effective cross sections σ_eff found from empirical analyses are about a factor 2.5 smaller than the usually accepted σ_eff = 15 mb. Here we discuss, which single-parton-scattering mechanisms can mimic the behavior of DPS induced production. Here especially the production of χ-pairs is important.