Model study on ϒ(nS) modification in small collision systems

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 the understanding of nuclear effects on the ϒ(nS) production. A theoretical calculation considering the gluo-dissociation and inelastic parton scattering for dissociation, and their inverse reaction for regeneration, reasonably describes the modification of ϒ(1S) in Pb+Pb collisions. Based on this calculation, a Monte Carlo simulation considering the dissociation effect 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 ϒ(nS) as a function of charged particle multiplicity (dNch/dη) and transverse momentum. We also calculate the elliptic flow of ϒ(nS) in small collision systems.