EMC effect and jet energy loss in relativistic deuteron-nucleus collisions

TL;DR

This paper examines how modifications in nuclear parton distribution functions affect high-pT hadron production in relativistic deuteron-nucleus collisions at RHIC and LHC, revealing discrepancies between pQCD predictions and experimental data.

Contribution

It provides a detailed analysis of the impact of nuclear PDF modifications, especially EMC effects, on high-pT hadron yields and compares different parameterizations with experimental results.

Findings

Nuclear PDF modifications have limited impact on observed suppression at RHIC.

pQCD models underestimate high-pT suppression in dAu collisions at RHIC.

Shadowing effects cause significant suppression at the LHC for pT < 100 GeV/c.

Abstract

We investigate the influence of modified nuclear parton distribution functions (PDFs) on high-pT hadron production at RHIC and LHC energies using a pQCD-improved parton model. For application at RHIC, we focus on the possible contribution of the EMC modification of the nuclear PDFs in the x > 0.3 region to the observed suppression of pi0 production at pT > 10 GeV/c in dAu collisions. We study three different parameterizations of the nuclear PDF modifications and find that they give consistent results for R_dAu(pT) for neutral pions in the region 10 GeV/c < pT < 20 GeV/c. We find that the EMC suppression of the parton distributions in the Au nucleus does not strongly influence the R_dAu for pi0 in the pT region where the suppression is observed. Using the HKN parameterization, we evaluate systematic errors in the theoretical R_dAu(pT) resulting from uncertainties in the nuclear PDFs. The measured nuclear modification factor is inconsistent with the pQCD model result for pT > 10 GeV/c even when the systematic uncertainties in the nuclear PDFs are accounted for. The inclusion of a small final-state energy loss can reduce the discrepancy with the data, but we cannot perfectly reproduce the pT dependence of the measured R_dAu(pT). For the LHC, we find that shadowing of the nuclear PDFs produces a large suppression in the yield of hadrons with pT < 100 GeV/c in p(d)A collisions.