Anisotropic Flow Measurements of Identified Particles in the STAR Experiment

TL;DR

This paper reports anisotropic flow measurements of identified particles in Au+Au collisions at various energies, revealing energy-dependent behaviors of flow coefficients and their relation to baryonic interactions.

Contribution

It provides the first detailed comparison of flow measurements at 3 GeV with higher energies, highlighting the role of baryonic mean-field potentials in low-energy collisions.

Findings

Positive $v_2$ and NCQ scaling at high energies

Negative $v_2$ and absence of NCQ scaling at 3 GeV

Baryonic mean-field potential reproduces low-energy flow features

Abstract

We report results of $v_1$ and $v_2$ for identified hadrons ($\pi^{\pm}, K^{\pm}, K_{S}^{0}, p, \phi$ and $\Lambda$) from Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV and $v_2$ for $\pi^{\pm}, K^{\pm}, p$ and $\bar{p}$ at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV using the STAR detector at RHIC. In Au+Au collisions at high energies, one finds that the values of $v_2$ are all positive and the number-of-constituent-quark (NCQ) scaling holds. On the other hand, results from collisions at 3 GeV, the midrapidity $v_2$ is negative for all hadrons and NCQ scaling is absent. In addition, the midrapidity $v_1$ slopes for all hadrons are found to be positive. Furthermore, the features of negative $v_2$ and positive $v_1$ slope at 3 GeV can be reproduced by calculations with baryonic mean-field potential in transport model. These results imply that in 3 GeV Au+Au collisions, the medium is characterized by baryonic interactions.