Checking Non-Flow Assumptions and Results via PHENIX Published Correlations in $p$$+$$p$, $p$$+$Au, $d$$+$Au, $^3$He$+$Au at $\sqrt{s_{NN}}$ = 200 GeV

TL;DR

This paper analyzes two-particle correlation data from RHIC collisions to evaluate non-flow effects and supports the interpretation of observed anisotropies as arising from initial geometry and hydrodynamic evolution, ruling out initial-state glasma explanations.

Contribution

It critically assesses non-flow correction methods and confirms that flow signals are dominated by initial geometry and final-state interactions, refining understanding of anisotropic flow origins.

Findings

Non-flow correction methods fail closure tests with models.

Adjusted flow coefficients suggest initial geometry dominance.

Higher v3/v2 ratio in p+Au indicates over-correction issues.

Abstract

Recently the PHENIX Collaboration has made available two-particle correlation Fourier coefficients for multiple detector combinations in minimum bias p+p and 0-5% central p+Au, d+Au, 3He+Au collisions at 200 GeV [1]. Using these coefficients for three sets of two-particle correlations, azimuthal anisotropy coefficients $v_2$ and $v_3$ are extracted for midrapidity charged hadrons as a function of transverse momentum. In this paper, we use the available coefficients to explore various non-flow hypotheses as well as compare the results with theoretical model calculations. The non-flow methods fail basic closure tests with AMPT and PYTHIA/ANGANTYR, particularly when including correlations with particles in the low multiplicity light-projectile going direction. In data, the non-flow adjusted $v_2$ results are modestly lower in p+Au and the adjusted $v_3$ results are more significantly higher in p+Au and d+Au. However, the resulting higher values for the ratio $v_3/v_2$ in p+Au at RHIC compared to p+Pb at the LHC is additional evidence for a significant over-correction. Incorporating these additional checks, the conclusion that these flow coefficients are dominated by initial geometry coupled with final-state interactions (e.g.~hydrodynamic expansion of quark-gluon plasma) remains true, and explanations based on initial-state glasma are ruled out. The detailed balance between intrinsic and fluctuation-driven geometry and the exact role of weakly versus strongly-coupled pre-hydrodynamic evolution remains an open question for triangular flow, requiring further theoretical and experimental investigation.