Energy dependence of $J/\psi$ production in Au+Au collisions at $\sqrt{s_{NN}} =$ 39, 62.4 and 200 GeV

TL;DR

This study measures $J/\psi$ production in Au+Au collisions at three energies, finding suppression in central collisions with no significant energy dependence, consistent with models including suppression and regeneration effects.

Contribution

It provides the first comprehensive comparison of $J/\psi$ suppression across multiple energies in a single experiment, highlighting the energy independence of nuclear modification factors.

Findings

$J/\psi$ suppression observed in central collisions at all energies.

No significant energy dependence of nuclear modification factors.

Results align with models including suppression and regeneration mechanisms.

Abstract

The inclusive $J/\psi$ transverse momentum ($p_{T}$) spectra and nuclear modification factors are reported at midrapidity ($|y|<1.0$) in Au+Au collisions at $\sqrt{s_{NN}}=$ 39, 62.4 and 200 GeV taken by the STAR experiment. A suppression of $J/\psi$ production, with respect to {\color{black}the production in $p+p$ scaled by the number of binary nucleon-nucleon collisions}, is observed in central Au+Au collisions at these three energies. No significant energy dependence of nuclear modification factors is found within uncertainties. The measured nuclear modification factors can be described by model calculations that take into account both suppression of direct $J/\psi$ production due to the color screening effect and $J/\psi$ regeneration from recombination of uncorrelated charm-anticharm quark pairs.