Strong Diffusion Effect of Charm Quarks on $J/\psi$ Production in Pb-Pb collisions at the LHC

Understand

We study the $J/\psi$ production based on coalescence model at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV Pb-Pb collisions.

• With the colliding energy increasing from 2.76 TeV to 5.02 TeV, the number of charm pairs is enhanced by more than 50%.
• However, the ratio of $J/\psi$ inclusive nuclear modification factors $R^{5.02TeV}_{AA}/R^{2.76TeV}_{AA}$ is only about 1.1 $\sim$ 1.2.
• We find that the regeneration of $J/\psi$ is proportional to the densities of charm and anti-charm quarks, instead of their total numbers.