ϒ(1S) transverse momentum spectra through dissociation and regeneration in heavy-ion collisions

We calculate the transition between a quarkonium state and an unbound heavy quark-antiquark pair through gluo-dissociation and inelastic parton scattering using a partonic picture that interpolates between the formal limits based on potential nonrelativistic QCD (pNRQCD) at different temperatures. While the thermal width increases with momentum and temperature, the quarkonium regeneration is affected by the heavy quark distribution function which depends on the diffusion constant. By solving the Boltzmann equation with the dissociation and regeneration terms, we investigate the medium modifications of quarkonium momentum spectra. Our numerical results indicate that the ϒ(1S) R_AA at high transverse momentum are influenced by the regeneration effects depending on the heavy quark diffusion. In this picture, the published CMS data that show an almost transverse momentum independence can be explained by the interplay between the suppression by dissociation and enhancement by regeneration at low and high transverse momenta, respectively. With the same input, we also calculate the transverse momentum dependence of the ϒ(1S) v₂ and show that it lies within the limits of the available data.