Speaker
Description
The suppression of quarkonium production in heavy-ion collisions has long been recognized as a key signature of QGP formation, reflecting the medium’s temperature and color-screening properties. However, interpreting the observed nuclear modification factor ($R_{AA}$) remains challenging due to the interplay between hot-medium effects, including dissociation and regeneration, and cold nuclear matter effects. Systematic measurements across different collision systems and energies are therefore essential for understanding how quarkonium production is modified by the evolving nuclear medium and advancing our understanding of QGP properties.
In this talk, we present measurements of the $J/\psi$ $R_{AA}$ as a function of centrality and transverse momentum in O+O collisions at $\sqrt{s_{\rm NN}} = 200$ GeV, and in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 14.6–27 GeV collected during the RHIC BES-II program. The O+O data probe a unique system-size regime, bridging the gap between small (p+p, p+Au) and large (Au+Au, U+U) collision systems, and provide an opportunity to study the system-size dependence of QGP effects. The Au+Au data at lower collision energies, where regeneration contributions are expected to be smaller, provide a cleaner probe of the primordial $J/\psi$ production and its modification by the hot medium. Together, these measurements provide crucial insight into the interplay of dissociation, regeneration, and cold nuclear matter effects across different collision systems and energies. We further discuss the energy dependence of $J/\psi$ $R_{AA}$ from RHIC to LHC energies and compare the results with theoretical model calculations.
