Multiplicity-dependent inclusive J/$\psi$ production at forward rapidity in pp collisions at $\mathbf{\sqrt{s} = 13}$ TeV

This paper presents a study of the inclusive forward $J/\psi$ yield as a function of forward charged-particle multiplicity in pp collisions at $\sqrt{s} =13$ TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative $J/\psi$ yields and relative charged-particle multiplicities with respect to these quantities obtained in inelastic collisions having at least one charged particle in the pseudorapidity range $|\eta| < 1$. The $J/\psi$ mesons are reconstructed via their decay into $\mu^+ \mu^-$ pairs in the forward rapidity region ($2.5 < y < 4$). The relative multiplicity is estimated in the forward pseudorapidity range which overlaps with the $J/\psi$ rapidity region. The results show a steeper-than-linear increase of the $J/\psi$ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.