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

TL;DR

This study measures how prompt and non-prompt J/ψ production varies with charged-particle multiplicity in proton-proton collisions at 13 TeV, revealing a stronger-than-linear increase especially in the emission direction.

Contribution

It provides the first detailed analysis of multiplicity dependence of prompt and non-prompt J/ψ yields, including azimuthal region segmentation, at LHC energies.

Findings

Both prompt and non-prompt J/ψ yields increase more than linearly with multiplicity.

The increase is strongest in the J/ψ emission direction region.

A weaker increase is observed in transverse and opposite azimuthal regions.

Abstract

The yields of prompt and non-prompt J/$\psi$ and the fraction of non-prompt J/$\psi$ are measured at midrapidity ($|y| < 0.9$) via the dielectron decay channel as a function of the midrapidity charged-particle multiplicity ($|\eta| < 0.9$) in pp collisions at $\sqrt{s} = 13$ TeV. The J/$\psi$ yields and the multiplicity are normalized by their average value in inelastic collisions. The multiplicity-dependent yield ratio between prompt J/$\psi$ and D$^0$ is reported. The multiplicity is further divided into three azimuthal regions with respect to the J/$\psi$ momentum: toward the J/$\psi$ emission direction, transverse, or opposite to it. A stronger-than-linear increase of the self-normalized yields is observed for both prompt and non-prompt J/$\psi$ production, with similar trends. This behaviour is also observed in the toward region, while a weaker increase is observed in the transverse and away regions.