Cold Nuclear Modifications at RHIC and LHC

TL;DR

This paper investigates nuclear modifications in high-energy collisions at RHIC and LHC using nuclear parton distribution functions within a pQCD framework, highlighting discrepancies with experimental data and predicting small enhancements without final-state effects.

Contribution

It applies recent nuclear parton distribution functions to calculate nuclear modification factors at RHIC and LHC, comparing results with experimental data and discussing the impact of final-state energy loss.

Findings

Deviations from unity in RHIC data are larger than model predictions.

Calculated R_{dAu}(p_T) slopes align with experimental data.

Small enhancement of R_{dPb}(p_T) predicted at LHC without final-state effects.

Abstract

We use recent nuclear parton distributions, among them the Hirai--Kumano--Nagai (HKN) and Eskola--Paukkunen--Salgado (EPS08) parameterizations, in our pQCD-improved parton model to calculate the nuclear modification factor, R_{AA'}(p_T), at RHIC and at the LHC. At RHIC, the deuteron-gold nuclear modification factor for pions, measured at p_T > 10 GeV/c in central collisions, appears to deviate more from unity than the model results. The slopes of the calculated R_{dAu}(p_T) are similar to the slopes of the PHENIX pion and photon data. At LHC, without final-state effects we see a small enhancement of R_{dPb}(p_T) in the transverse momentum range 10 GeV/c < p_T < 100 GeV/c for most parameterizations. The inclusion of final-state energy loss will reduce the R_{dPb}(p_T) values.