Momentum spectra of bottomonium in heavy-ion collisions

The early universe consisted of a dense nuclear medium that took a short time to expand and form hadrons; this medium is called the quark-gluon plasma (QGP). It is believed that a QGP can be created in URHICs, and that heavy quarks created early in the collision act as a probe of the QGP. We investigate models of producing bottomonium ($b\bar{b} \to Y$) states in URHICs at RHIC and LHC energies in order to describe the regeneration of bottomonia from the QGP as it depends on transverse momentum ($ p_T $). To simulate the evolution of the bottomonium abundance in URHICs, we rely on the results of a kinetic rate equation approach, which describes the number of bottomonia $ N_Y $ as it approaches equilibrium. We first implement a blastwave model to estimate the $ p_T$-spectra of locally thermalized $ \Upsilon^{1S} $ and $ \Upsilon^{2S} $ states, boosted by a flow field. However, since bottomonium is not fully thermalized in the QGP, we employ a quark coalescence model with realistic $ b$-quark spectra in the calculation of its in-medium distributions. Finally, the total nuclear modification factor ($ R_{AA}(p_T) $) is calculated accounting for the interplay of suppression and regeneration mechanisms of bottomonium in URHICs as compared to proton-proton collisions.