Gluon saturation effects on the color singlet J/Psi production in high energy dA and AA collisions

TL;DR

The paper develops a CGC-based, color-singlet treatment of $J/\\psi$ production in high-energy pA and AA collisions, deriving cross sections that respect parity constraints and include possible color-octet to singlet transitions inside the nucleus. It extends from a quasi-classical description to include BK evolution for rapidity/energy dependence and tests two dipole models (DHJ, bCGC) against RHIC and LHC data. The results show that cold nuclear matter effects can describe $J/\\psi$ production in pA/dA, but AA data require additional final-state interactions (e.g., color screening or dissociation) to reproduce suppression/enhancement patterns. The work provides concrete cross-section formulas and model-based predictions for future $pA$ runs at the LHC and offers a CGC framework for quantifying color glass condensate effects in heavy-ion collisions.

Abstract

We derive the formulae for the cross section of J/Psi production in high energy pA and AA collisions taking into account the gluon saturation/color glass condensate effects. We then perform the numerical calculations of the corresponding nuclear modification factors and find a good agreement between our calculations and the experimental data on J/Psi production in dA collisions. We also observe that cold nuclear modification effects alone cannot describe the data on J/Psi production in AA collisions. Additional final state suppression (at RHIC) and enhancement (at LHC) mechanisms are required to explain the experimental observations.

Figures (4)

• Figure 1: Smaple diagram contributing to the $gA\to J/\psi$ process. The point of the last inelastic interaction is signaled explicitly at the longitudinal coordinate $\xi$.
• Figure 2: Lowest order process in gluon induced $J/\psi$ production. Color indices are indicated explicitly.
• Figure 3: Nuclear modification factor vs $N_\mathrm{part}$ in (a) $dAu$ and (b) $AA$ collisions using the DHJ model Dumitru:2005kb. Band 'a' (green) represents rapidity $y=-1.7$ at $\sqrt{s}=200$ GeV, 'b' (blue): $y=0$, $\sqrt{s}=200$ GeV, 'c' (red): $y=1.7$, $\sqrt{s}=200$ GeV, 'd' (brown): $y=3.25$, $\sqrt{s}=2.76$ TeV, 'e' (cyan): $y=0$, $\sqrt{s}=5.5$ TeV. $m=1.5$ GeV, $C=1$. Experimental data Adler:2005phAdare:2006nsAdare:2011yfPillot:2011zg is represented by (blue) circles in 'b', by (red) squares in 'c' and by (brown) triangles in 'd'. (Color online).
• Figure 4: Same as Fig. \ref{['fig:dhj']} using the bCGC model Kowalski:2006hc.