EMMI Workshop: Mining for gluon saturation at the LHC and the future EIC

Quarkonia -- bound states of heavy quark-antiquark pairs (charm or bottom) -- offer a unique probe of both perturbative and non-perturbative QCD. While the hard-scale production of the quark-antiquark pairs is calculable via perturbation theory, their hadronization into bound states requires non-perturbative models like NRQCD. In hadronic collisions, the underlying event activity, usually quantified in terms of charged-particle multiplicity density, is mainly determined by soft particle production processes. By correlating measurements of quarkonium production and event activity in small systems, we can learn more about the interplay between hard and soft particle production from initial-state effects, such as gluon saturation or Multiple Partonic Interactions, or from final-state effects. In addition, separating prompt and non-prompt J/$\psi$ helps to study separately the charm and beauty sectors. Finally, measuring the multiplicity in different azimuthal regions with respect to the J/$\psi$ emission direction allows to disentangle the effects of the particles emitted in the same production process as the J/$\psi$ from the effects of the underlying event.

In this talk, recent measurements of prompt and non-prompt J/$\psi$ production by the ALICE Collaboration at midrapidity as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}=13$ TeV will be presented.