Centrality and pT dependence of J/psi suppression in proton-nucleus collisions from parton energy loss

TL;DR

This paper addresses the mechanism behind J/ψ suppression in proton–nucleus collisions by isolating cold nuclear matter effects, proposing that parton energy loss induced by transverse momentum broadening dominates the observed patterns. It develops a double-shift formalism that relates p–A to p–p production via an energy loss $\varepsilon$ and a broadening $\Delta p_\perp$, governed by the quenching weight ${\cal P}(\varepsilon,E)$ and a transport coefficient-based broadening $\ell_{\perp A}^2=\hat q_A L_A$. The model, with a fixed $\hat q_0=0.075$ GeV$^2$/fm, successfully describes E866 and PHENIX data across rapidities and centralities, and it yields clear predictions for J/ψ and Υ production in LHC p–Pb collisions. The good agreement across a broad kinematic range supports momentum-broadening–driven energy loss as the dominant cold nuclear matter effect in J/ψ suppression and provides a robust baseline for interpreting hot-medium effects in heavy-ion collisions. The work offers precise, testable predictions for upcoming LHC measurements and highlights the practical utility of the quenching-weight and centrality–dependent path-length framework."

Abstract

The effects of parton energy loss and pT-broadening in cold nuclear matter on the pT and centrality dependence, at various rapidities, of J/psi suppression in p-A collisions are investigated. Calculations are systematically compared to E866 and PHENIX measurements. The very good agreement between the data and the theoretical expectations further supports pT-broadening and the associated medium-induced parton energy loss as dominant effects in J/psi suppression in high-energy p-A collisions. Predictions for J/psi (and Upsilon) suppression in p-Pb collisions at the LHC are given.

Figures (7)

• Figure 1: Comparison between heavy-quarkonium (${\mathrm J}/\psi$, $\Upsilon$) production data in p--p collisions and the parametrization (\ref{['pp-fit-2d']}) (solid red line). Data are taken from ATLAS Aad:2011sp, LHCb Aaij:2011jhLHCb:2012aa, and PHENIX Adare:2006kf.
• Figure 2: Model predictions (solid red curves) for the ${\mathrm J}/\psi$ nuclear suppression factor compared to the E866 data for $R_{\rm Fe/Be}(p_{\perp})$ (left) and $R_{\rm W/Be}(p_{\perp})$ (right), in the intermediate-$x_{_F}$ ($\langle{x_{_F}}\rangle = 0.308$, top) and large-$x_{_F}$ ($\langle{x_{_F}}\rangle = 0.48$, bottom) ranges. The dashed lines indicate the effect of momentum broadening only, $R_{\rm pA}^{\rm broad}(y, p_{\perp})$, Eq. (\ref{['eq:rpabroad']}).
• Figure 3: Model predictions for the ${\mathrm J}/\psi$ nuclear suppression factor $R_{\rm pA}(p_{\perp})$ in minimum bias d--Au collisions at RHIC, at backward (left), central (middle) and forward (right) rapidities (solid curves). The dashed lines indicate the effect of momentum broadening only, $R_{\rm pA}^{\rm broad}(y, p_{\perp})$, Eq. (\ref{['eq:rpabroad']}).
• Figure 4: Same as Fig. \ref{['fig:RHIC-minbias']} in the four centrality classes (from top left to bottom right in each panel) at backward, central and forward rapidities (upper left, upper right, bottom).
• Figure 5: Prediction for the ${\mathrm J}/\psi$ nuclear suppression factor $R_{\rm pA}(p_{\perp})$ in minimum bias p--Pb collisions at LHC, for backward, central and forward rapidities.