Event anisotropy $v_{2}$ in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7 - 62.4 GeV with STAR

TL;DR

This study measures the elliptic flow parameter $v_2$ in gold-gold collisions across a range of energies, revealing energy-dependent differences between particles and antiparticles, and examining the scaling behavior of identified hadrons.

Contribution

It provides detailed $v_2$ measurements at multiple energies and explores the particle-antiparticle differences and NCQ scaling, extending understanding of the quark-gluon plasma properties.

Findings

Significant $v_2$ differences between particles and antiparticles below 39 GeV.

Observed stronger differences for baryons than mesons.

Energy dependence of $v_2$ and deviations from NCQ scaling.

Abstract

We present the $v_2$ measurement at midrapidity from Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV for inclusive charged hadrons and identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $K_{S}^{0}$, $p$, $\bar{p}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, $\bar{\Omega}^{+}$) up to 4 GeV/$c$ in $p_{T}$. The beam energy and centrality dependence of charged hadron $v_2$ are presented with comparison to higher energies at RHIC and LHC. The identified hadron $v_{2}$ are used to discuss the NCQ scaling for different beam energies. Significant difference in $v_{2}(p_{T})$ is observed between particles and corresponding anti-particles for $\sqrt{s_{NN}} <$ 39 GeV. These differences are more pronounced for baryons compared to mesons and they increase with decreasing energy.