Probing hot QCD medium with heavy quarkonium in small and large collision systems

Abstract

The yield ratios of different heavy-quarkonium states serve as sensitive probes of final-state interactions in relativistic nuclear collisions, because common cold-nuclear-matter effects are expected to be substantially reduced in these ratios. To quantify hot QCD medium effects in small collision systems, such as proton-nucleus collisions, we employ a time-dependent Schrodinger equation framework to consistently simulate the real-time evolution of both bottomonium and charmonium states in the presence of in-medium complex heavy-quark potentials. In p-Pb collisions at sqrt(sNN) = 8.16 TeV, our model successfully describes the observed suppression in the yield ratios of excited-to-ground states, specifically Upsilon(nS)/Upsilon(1S) and psi(2S)/J/psi, as a function of charged-particle multiplicity. This agreement supports the formation of a transient, hot QCD medium in small systems. Furthermore, the framework is employed to study the ratio of bottomonium nuclear modification factors in sqrt(sNN) = 5.02 TeV Pb-Pb collisions, where hot medium effects become stronger. By establishing a unified description across two distinct heavy-quark flavors and different collision systems, our study indicates that the yield ratio of bottomonium states serves as a comparatively clean probe of the hot QCD medium generated in small collision systems.

Comments: 7 pages,5 figures