The RHIC azimuth quadrupole: "perfect liquid" or gluonic radiation?

TL;DR

This paper questions the interpretation of large elliptic flow at RHIC as perfect liquid behavior, proposing instead that the azimuth quadrupole may originate from gluonic radiation, based on detailed correlation analysis.

Contribution

It introduces a new perspective on the azimuth quadrupole, suggesting a gluonic radiation origin rather than hydrodynamic flow, supported by 2D angular autocorrelation analysis.

Findings

Contradicts conventional flow interpretations with correlation data.

Shows azimuth quadrupole depends on initial parton geometry.

Suggests gluonic multipole radiation as the source of the quadrupole.

Abstract

Large elliptic flow at RHIC seems to indicate that ideal hydrodynamics provides a good description of Au-Au collisions, at least at the maximum RHIC energy. The medium formed has been interpreted as a nearly perfect (low-viscosity) liquid, and connections have been made to gravitation through string theory. Recently, claimed observations of large flow fluctuations comparable to participant eccentricity fluctuations seem to confirm the ideal hydro scenario. However, determination of the azimuth quadrupole with 2D angular autocorrelations, which accurately distinguish ``flow'' (quadrupole) from ``nonflow'' (minijets), contradicts conventional interpretations. Centrality trends may depend only on the initial parton geometry, and methods used to isolate flow fluctuations are sensitive instead mainly to minijet correlations. The results presented in this paper suggest that the azimuth quadrupole may be a manifestation of gluonic multipole radiation.