Checking nonflow assumptions and results via PHENIX published correlations in p plus p, p plus Au, d+Au, and 3He+Au at √sNN=200 GeV

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, and 3 He +Au collisions at root s(NN) = 200 GeV [Phys. Rev. C 105, 024901 (2022)]. 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 nonflow hypotheses as well as to compare the results with theoretical model calculations. The nonflow 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 nonflow 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 overcorrection. 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 solely 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 prehydrodynamic evolution remains an open question for triangular flow, requiring further theoretical and experimental investigation.

Automated summary

The PHENIX Collaboration has extracted the azimuthal anisotropy coefficients v2 and v3 for midrapidity charged hadrons as a function of transverse momentum in p+p and p+Au, d+Au, and 3 He +Au collisions. They explored nonflow hypotheses and compared the results with theoretical model calculations. The findings indicate that the flow coefficients are dominated by initial geometry and final-state interactions, ruling out explanations solely based on the initial-state glasma.