Characterizing radial flow fluctuations in relativistic heavy-ion collisions at top RHIC and LHC energies

This study presents a systematic investigation of the transverse-momentum differential radial flow fluctuations observable v 0 ( p T ) in relativistic heavy-ion collisions at top Relativistic Heavy Ion Collider ( s N N = 200 GeV) and Large Hadron Collider ( s N N = 2.76 and 5.02 TeV) energies. Using a multistage hydrodynamic model, this study assesses the sensitivity of v 0 ( p T ) to a wide range of physical effects, including bulk and shear viscosities, off-equilibrium corrections at particlization, the presence of a hadronic afterburner, and the nucleon size in the initial conditions. By employing complementary rescaling strategies, this study demonstrates how different physical effects leave distinct imprints on the shape of v 0 ( p T ) . A combined double-rescaling of v 0 ( p T ) / v 0 versus p T / 〈 p T 〉 reveals a universality across a wide range of energies and model assumptions in the low- p T regime, a robust signature of collective behavior. This allows us to disentangle the universal dynamics of the bulk medium from model-specific features that emerge at higher p T . These results establish v 0 ( p T ) as a powerful and complementary observable for constraining quark-gluon plasma transport properties and initial-state granularity, offering a unique probe of the created QCD medium.