Model study on $\Upsilon(nS)$ modification in small collision systems

TL;DR

This paper develops a model and Monte Carlo simulation to study the modification of $$ production in small collision systems, aiming to understand nuclear effects and potential medium influences on quarkonium suppression.

Contribution

It extends existing models to small systems like p+p, p+Pb, p+O, and O+O collisions, incorporating medium effects and event-by-event fluctuations for $(nS)$ production analysis.

Findings

Quantifies nuclear modification factor of $(nS)$ as a function of multiplicity and transverse momentum.

Calculates elliptic flow of $(nS)$ in small systems.

Provides insights into medium effects in small collision systems.

Abstract

Quarkonium production has been studied extensively in relativistic heavy-ion collision experiments to understand the properties of the quark gluon plasma. The experimental results on the yield modification in heavy-ion collisions relative to that in $p$+$p$ collisions can be described by several models considering dissociation and regeneration effects. A yield modification beyond initial-state effects has also been observed in small collision systems such as $p$+Au and $p$+Pb collisions, but it is still premature to claim any hot medium effect. A model study in various small collision systems such as $p$+$p$, $p$+Pb, $p$+O, and O+O collisions will help quantitatively understanding nuclear effects on the $\Upsilon(nS)$ production. A theoretical calculation considering the gluo-dissociation and inelastic parton scattering and their inverse reaction reasonably describes the suppression of $\Upsilon(1S)$ in Pb+Pb collisions. Based on this calculation, a Monte-Carlo simulation is developed to more realistically incorporate the medium produced in heavy-ion collisions with event-by-event initial collision geometry and hydrodynamic evolution. We extend this framework to small systems to study the medium effects. In this work, we quantify the nuclear modification factor of $\Upsilon(nS)$ as a function of charged particle multiplicity ($dN_{ch}/d\eta$) and transverse momentum. We also calculate the elliptic flow of $\Upsilon(nS)$ in small collision systems.