Abstract
The inclusive J/ψ transverse momentum spectra and nuclear modification factors are reported at mid-rapidity (|y|<1.0) in Au+Au collisions at sNN = 39, 62.4 and 200 GeV taken by the STAR experiment. A suppression of J/ψ production, with respect to 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/ψ production due to the color screening effect and J/ψ regeneration from recombination of uncorrelated charm–anticharm quark pairs.
Highlights
The Relativistic Heavy Ion Collider (RHIC) was built to investigate strongly interacting matter at high temperature and energy density in the laboratory through high-energy heavy-ion collisions
The shaded and hatched bands indicate the uncertainties on the baseline J /ψ cross section in p + p collisions [50,59,60] and T A A, respectively
The dotted and hatched bands indicate the uncertainties on the baseline J /ψ cross section in p + p collisions [50,59,60] and T A A, respectively
Summary
The Relativistic Heavy Ion Collider (RHIC) was built to investigate strongly interacting matter at high temperature and energy density in the laboratory through high-energy heavy-ion collisions. A stronger suppression at forward rapidity (1.2 < | y| < 2.2) compared to mid-rapidity (| y| < 0.35) was observed at RHIC [16] These observations indicate that effects other than color screening are important for J /ψ production. With the higher temperature and density at RHIC, the increased contribution due to regeneration from the larger charm quark density could compensate for the enhanced suppression. Measurements of J /ψ invariant yields at different collision energies at RHIC in different centralities at mid-rapidity can shed new light on the interplay of the mechanisms for J /ψ production and medium properties. We further study the collision energy dependence of J /ψ production and test the hypothesis of the two competing mechanisms of color screening and regeneration.
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