QCD Saturation and Deuteron-Nucleus Collisions

TL;DR

The paper addresses hadron multiplicities in deuteron-nucleus collisions at RHIC within the Color Glass Condensate/saturation framework (KLN model). It derives a semi-analytic expression for $dN/dy$ using two saturation scales, unintegrated gluon distributions, and Glauber geometry, predicting $N_{part}$ scaling in different rapidity regions and centrality dependence. Normalization uncertainties are discussed, including the gluon liberation coefficient and the proton saturation scale, and predictions are compared with RHIC data and other systems. An erratum later shows that remaining discrepancies with $d$-Au data mainly arise from centrality determination (optical vs MC Glauber) and a revised proton $Q_s^2$ improves the fit, underscoring the sensitivity to centrality modeling and supporting CGC viability for high-density QCD in $dA$ collisions.

Abstract

We make quantitative predictions for the rapidity and centrality dependencies of hadron multiplicities in dA collisions at RHIC basing on the ideas of parton saturation in the Color Glass Condensate.

Figures (6)

• Figure 1: Dependence of the number of participants from the deuteron $N_{part}(Deuteron)$ on the number of participants in the $Au$ nucleus $N_{part}(Gold)$ for $W = 200$ GeV.
• Figure 2: Rapidity dependence $dN/d\eta$ of charged hadron multiplicities in deuteron - gold collision for different centrality cuts; also shown is the minimum bias distribution ($0-100 \%$).
• Figure 3: $N_{part}$ dependence for positive ($d$ fragmentation region) rapidities for deuteron-gold interactions at $W = 200$ GeV.
• Figure 4: $N_{part}^{Au}$ dependence for negative ($Au$ fragmentation region) rapidities for deuteron-gold interactions at $W = 200$ GeV.
• Figure 5: Rapidity dependence for $dN/d\eta$ for proton - antiproton collision at $W = 200$ and $546$ GeV. The solid lines correspond to Eq. (\ref{['MSTR1']}) with both saturation scales set equal to the proton one. The data is taken from PDG.