J/ψ suppression and p T spectra in RHIC and LHC energy collisions

Abstract

In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy, $\sqrt{s}=200$ GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T J/ψ. Sequential melting of charmonium states (χ c , ψ ′ and J/ψ), with melting temperatures $T_{\chi_{c}}=T_{\psi^{\prime}}\approx1.2T_{c}$ , T J/ψ≈2T c and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ p T spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ p T spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy, $\sqrt{s}=5500$ GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ p T distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC.