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Centrality, Rapidity and Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in d+Au, Cu+Cu and Au+Au Collisions at sqrt(s_NN)=200 GeV

E. G. Ferreiro, F. Fleuret, J. P. Lansberg, A. Rakotozafindrabe

TL;DR

This paper probes cold nuclear matter effects on J/ψ production at RHIC by contrasting intrinsic (2→1) and extrinsic (2→2) production schemes within a Glauber-Mock framework. It systematically studies gluon shadowing using multiple nPDF parametrisations (EKS98, EPS08, nDSg) with a local density dependence and couples them to an effective nuclear absorption σ_abs, fitted to d+Au data, to predict R_dAu, R_CP, and R_AA across rapidity, centrality, and transverse momentum for d+Au, Cu+Cu, and Au+Au collisions. A key finding is that 2→2 kinematics shift the anti-shadowing peak to higher rapidity and modify the inferred σ_abs values, with extrinsic production generally requiring larger absorption to match data; this has important implications for disentangling CNM from hot-medium effects in heavy-ion collisions. Overall, the work provides a cohesive framework for CNM corrections, constraining gluon shadowing and absorption, and informing the interpretation of J/ψ suppression in nucleus-nucleus environments at RHIC and beyond.

Abstract

We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We have studied the effects of three different gluon-shadowing parametrisations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/Psi is neglected as well as an exact kinematics for a 2 -> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R_dAu, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 -> 2 kinematics, irrespective of which shadowing parametrisation is used. In turn, we have noted differences in the effective final-state nuclear absorption necessary to fit the PHENIX d+Au data. Taking advantage of our implementation of a 2 -> 2 kinematics, we have also computed the transverse momentum dependence of the latter nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for Cu+Cu and Au+Au collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of R_CP in d+Au by the PHENIX collaboration.

Centrality, Rapidity and Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in d+Au, Cu+Cu and Au+Au Collisions at sqrt(s_NN)=200 GeV

TL;DR

This paper probes cold nuclear matter effects on J/ψ production at RHIC by contrasting intrinsic (2→1) and extrinsic (2→2) production schemes within a Glauber-Mock framework. It systematically studies gluon shadowing using multiple nPDF parametrisations (EKS98, EPS08, nDSg) with a local density dependence and couples them to an effective nuclear absorption σ_abs, fitted to d+Au data, to predict R_dAu, R_CP, and R_AA across rapidity, centrality, and transverse momentum for d+Au, Cu+Cu, and Au+Au collisions. A key finding is that 2→2 kinematics shift the anti-shadowing peak to higher rapidity and modify the inferred σ_abs values, with extrinsic production generally requiring larger absorption to match data; this has important implications for disentangling CNM from hot-medium effects in heavy-ion collisions. Overall, the work provides a cohesive framework for CNM corrections, constraining gluon shadowing and absorption, and informing the interpretation of J/ψ suppression in nucleus-nucleus environments at RHIC and beyond.

Abstract

We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We have studied the effects of three different gluon-shadowing parametrisations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/Psi is neglected as well as an exact kinematics for a 2 -> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R_dAu, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 -> 2 kinematics, irrespective of which shadowing parametrisation is used. In turn, we have noted differences in the effective final-state nuclear absorption necessary to fit the PHENIX d+Au data. Taking advantage of our implementation of a 2 -> 2 kinematics, we have also computed the transverse momentum dependence of the latter nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for Cu+Cu and Au+Au collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of R_CP in d+Au by the PHENIX collaboration.

Paper Structure

This paper contains 18 sections, 5 equations, 11 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Our approach
  3. Partonic process for $c \bar{c}$ production
  4. Shadowing
  5. The nuclear absorption
  6. Results for $\rm dAu$ collisions
  7. $R_{dAu}$ vs rapidity: distribution shift
  8. $R_{dAu}$ vs centrality
  9. $R_{dAu}$ vs transverse momentum
  10. $R_{CP}$
  11. Results for $\rm CuCu$ and $\rm AuAu$ collisions
  12. Centrality dependence
  13. Rapidity dependence
  14. Transverse-momentum dependence
  15. Extraction of break-up cross section by fits on $d$Au data
  16. ...and 3 more sections

Figures (11)

  • Figure 1: (Color online) comparison of the gluon shadowing parametrisations EKS98 Eskola:1998df, EPS08 Eskola:2008ca, nDS deFlorian:2003qf at LO and EPS09 Eskola:2009uj at LO in a Lead nucleus at $Q^2=1.69$ GeV$^2$. Adapted from Eskola:2009uj.
  • Figure 2: (Color online) $J/\psi$ nuclear modification factor in $d$Au collisions, $R_{dAu}$, at $\sqrt{s_{NN}}=200\mathrm{~GeV}$ versus $y$ in the intrinsic (top row) and extrinsic (lower row) schemes using the following gluon shadowing parametrisations: EKS98 Eskola:1998df (left), EPS08 Eskola:2008ca (middle), nDSg deFlorian:2003qf (right). The vertical lines indicate qualitatively the antishadowing peak and its shifts towards larger $y$ in the extrinsic scheme.
  • Figure 3: (Color online) $J/\psi$ nuclear modification factor in $d$Au collisions, $R_{dAu}$, at $\sqrt{s_{NN}}=200\mathrm{~GeV}$ versus the number of collisions for three rapidity ranges and for four values of the nuclear absorption (from top to bottom: $\sigma_{abs}=$0, 2, 4 and 6 mb) using a) EKS98, b) EPS08 and c) nDSg in the extrinsic scheme.
  • Figure 4: (Color online) $J/\psi$ nuclear modification factor in $d$Au collisions, $R_{dAu}$, at $\sqrt{s_{NN}}=200\mathrm{~GeV}$ versus the transverse momentum for three rapidity ranges and for four values of the nuclear absorption (from top to bottom: $\sigma_{abs}=$0, 2, 4 and 6 mb) using a) EKS98, b) EPS08 and c) nDSg in the extrinsic scheme.
  • Figure 5: (Color online) $J/\psi$ central to peripheral nuclear modification factor in $d$Au collisions, $R_{CP}$, at $\sqrt{s_{NN}}=200\mathrm{~GeV}$ versus rapidity for three centrality ranges and for four values of the nuclear absorption (from top to bottom: $\sigma_{abs}=$0, 2, 4 and 6 mb) using : a) EKS98, b) EPS08, c) nDSg.
  • ...and 6 more figures