Centrality dependence of identified particle elliptic flow in relativistic heavy ion collisions at sqrt(s)= 7.7--62.4 GeV

TL;DR

This study measures how the elliptic flow of identified particles varies with collision centrality in heavy ion collisions at energies from 7.7 to 62.4 GeV, revealing patterns consistent with quark scaling and centrality effects.

Contribution

It provides new measurements of elliptic flow at 14.5 GeV and explores the centrality dependence across a range of energies, enhancing understanding of the quark-gluon plasma.

Findings

Similar baryon-meson v_2 splitting across centralities, consistent with quark scaling.

Largest v_2 differences between particles and antiparticles occur in central collisions.

Data agree with transport and blast wave models.

Abstract

Elliptic flow (v_2) values for identified particles at midrapidity in Au + Au collisions measured by the STAR experiment in the Beam Energy Scan at the Relativistic Heavy Ion Collider at sqrt{s_{NN}}= 7.7--62.4 GeV are presented for three centrality classes. The centrality dependence and the data at sqrt{s_{NN}}= 14.5 GeV are new. Except at the lowest beam energies we observe a similar relative v_2 baryon-meson splitting for all centrality classes which is in agreement within 15% with the number-of-constituent quark scaling. The larger v_2 for most particles relative to antiparticles, already observed for minimum bias collisions, shows a clear centrality dependence, with the largest difference for the most central collisions. Also, the results are compared with A Multiphase Transport Model and fit with a Blast Wave model.