Understanding RHIC Collisions: Modified QCD fragmentation vs quark coalescence from a thermalized flowing medium

TL;DR

This paper compares modified QCD fragmentation and quark coalescence models to interpret RHIC collision data, emphasizing the dominance of parton scattering and fragmentation over hydrodynamic flow in central Au-Au collisions.

Contribution

It provides a detailed analysis contrasting QCD fragmentation and quark coalescence models, highlighting the prominence of parton fragmentation in RHIC collision outcomes.

Findings

Parton scattering and fragmentation dominate RHIC collisions.

Hard component in spectra aligns with pQCD predictions.

Minijets survive in central collisions, indicating less thermalization.

Abstract

The hydrodynamic (hydro) model applied to data from the relativistic heavy ion collider (RHIC) suggests that a dense QCD medium opaque to partons is formed in more-central Au-Au collisions. However, two-component spectrum analysis reveals a hard component, consistent with parton fragmentation described by pQCD, which can masquerade as "radial flow." Minimum-bias angular correlations reveal that most scattered partons survive as "minijets" even in central Au-Au collisions. Such alternative methods quantitatively describe spectrum and correlation structure via pQCD calculations. RHIC collisions appear to be dominated by parton scattering and fragmentation even in central Au-Au collisions.