Elliptic flow of π⁰ mesons in Cu+Au collisions at √s__NN=200 GeV and U+U at √s__NN=193 GeV

2026/08/03 by PHENIX Collaboration, N. J. Abdulameer, U. Acharya +380
Physics and Astronomy · #nucl-ex

paper · pdf

325 authors from 74 institutions, 14 pages, 10 figures, 3 tables. v1 is version submitted to Physical Review C. HEPdata tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

arxiv created 2026/08/03 · arxiv updated 2026/08/05

Abstract

The second-order azimuthal anisotropy coefficients (v₂) of neutral π mesons (π⁰) have been measured as a function of the transverse momentum (p_T) and centrality of Cu+Au collisions at √s__NN=200~GeV and U+U at √s__NN=193 GeV at the Relativistic Heavy Ion Collider. The analysis used experimental data collected by the PHENIX experiment at midrapidity |η|<0.35 over a broad p_T range up to ≈10~GeV/c, and the obtained results are compared with previous PHENIX measurements in Au+Au collisions at √s__NN=200~GeV. In all three collision systems, the π⁰~v₂ values follow the scaling with the second-order participant eccentricity and the cube root of the number of participating nucleons (ε₂ N_{\rm part}^1/3) up to ≈4~GeV/c. Furthermore, the behavior of the azimuthal-dependent π⁰ nuclear-modification factors and associated fractional parton-energy losses are evaluated from measured nonzero v₂ values of π⁰ at p_T>5 GeV/c and found to be approximately the same for similar values of N_{\rm part}^1/3 in these collision systems. These findings demonstrate that the mechanism of π⁰ v₂ generation exhibits a high degree of universality across different initial geometries of heavy-ion collisions.

Citations

• The PHENIX Forward Silicon Vertex Detector
• Collective Flow and Viscosity in Relativistic Heavy-Ion Collisions
• Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions
• Multiplicity, average transverse momentum and azimuthal anisotropy in U+U collisions at √s_NN = 200 GeV using AMPT model
• Predictions of elliptic flow and nuclear modification factor from 200 GeV U + U collisions at RHIC
• Systematic comparison of jet energy-loss schemes in a realistic hydrodynamic medium
• Inclusive cross section and double helicity asymmetry for π⁰ production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
• Anisotropic flow and jet quenching in ultra-relativistic U+U collisions
• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• JET QUENCHING AND RADIATIVE ENERGY LOSS IN DENSE NUCLEAR MATTER
• High p_T Azimuthal Asymmetry in Non-central A+A at RHIC
• Jet Quenching and Azimuthal Anisotropy of Large p_T Spectra in Non-central High-energy Heavy-ion Collisions
• Methods for analyzing anisotropic flow in relativistic nuclear collisions
• Proton and Pion Production Relative to the Reaction Plane in Au + Au Collisions at AGS Energies