Multiplicity dependence of J/$\psi$ production at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This study measures how the production of J/ψ mesons in proton-proton collisions at 13 TeV varies with charged-particle multiplicity, revealing a stronger-than-linear increase and comparing results with theoretical models.

Contribution

It provides the first detailed measurement of J/ψ yield dependence on multiplicity at midrapidity in pp collisions at 13 TeV, highlighting non-linear behavior.

Findings

J/ψ yield increases more than linearly with charged-particle multiplicity.

The dependence varies with transverse momentum.

Theoretical models describe the trend but not always quantitatively.

Abstract

Measurements of the inclusive J/$\psi$ yield as a function of charged-particle pseudorapidity density ${\rm d}N_{\rm ch}/\rm{d}\eta$ in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE at the LHC are reported. The J/$\psi$ meson yield is measured at midrapidity ($|y|<0.9$) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity ($|\eta|<1$) and at forward rapidity ($-3.7<\eta<-1.7$ and $2.8<\eta<5.1$); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/$\psi$ yield with normalized ${\rm d}N_{\rm ch}/\rm{d}\eta$ is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively.