2025/12/08 by Thomas A. Trainor, Trainor, Thomas A.
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Particle Detector Development and Performance
paper · pdf · doi:10.48550/arxiv.2512.08003
pt-differential quantity v2(pt) is meant to measure elliptic flow manifested by a dense QCD medium formed in high-energy nucleus-nucleus collisions. Elliptic flow may be referred to more neutrally as a cylindrical quadrupole component of the transverse motion of particle sources within a collision. As defined, v2(pt) relies on an implicit assumption that almost all produced particles emerge from a single source. This article describes a detailed study of the algebraic structure of v2(pt). A procedure is developed to derive a common monopole boost (radial flow) value and quadrupole pt spectra for several hadron species. The method is applied to v2(pt) data for three hadron species from 2.76 TeV Pb-Pb collisions. According to available v2(pt) data the assumption of a single dominant particle source within A-A collisions is unjustified. Combined with a previous study of quadrupole amplitude variation for 200 GeV p-p collisions these results demonstrate that quadrupole structure is related to a novel QCD process separate from projectile-nucleon dissociation and jet production. Given quadrupole evolution it is unlikely that a hydrodynamic description is relevant to that process.