Nuclear modification of the J/Psi transverse momentum distributions in high energy pA and AA collisions

TL;DR

This paper investigates the transverse momentum distribution of J/Psi particles in high-energy pA and AA collisions, highlighting the limitations of cold nuclear matter effects and suggesting the need for additional suppression mechanisms, especially at semi-hard momenta.

Contribution

The study provides a comprehensive evaluation of initial state effects on J/Psi production using the QCD dipole model across different energies and kinematic regions, emphasizing the importance of final state effects.

Findings

Cold nuclear matter effects alone cannot explain experimental data.

Discrepancies increase at semi-hard transverse momenta.

Final state effects are significant in J/Psi suppression.

Abstract

We evaluate the transverse momentum spectrum of J/Psi (up to semi-hard momenta) in pA and AA collisions taking into account only the initial state effects, but resumming them to all orders in \alpha_s^2 A^{1/3}. In our previous papers we noticed that cold nuclear matter effects alone could not explain the experimental data on rapidity and centrality dependencies of the J/Psi yield in AA collisions indicating the existence of an additional suppression mechanism. Our present calculations indicate that the discrepancy persists and even increases at semi-hard transverse momenta, implying a significant final state effect on J/Psi production in this kinematical domain. The QCD dipole model we employ is only marginally applicable for J/Psi production at mid-rapidity at RHIC energies but its use is justified in the forward rapidity region. At LHC energies we can quantitatively evaluate the magnitude of cold nuclear matter effects in the entire kinematical region of interest. We present our calculations of J/Psi transverse momentum spectra in pA and AA collisions at LHC and RHIC energies.