The elliptic flow in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV at STAR

TL;DR

This paper measures elliptic flow in gold-gold collisions at various energies, revealing differences between baryons and anti-baryons and lower $ ext{v}_2$ for $ ext{phi}$ mesons at 11.5 GeV, providing insights into the quark-gluon plasma.

Contribution

First systematic comparison of elliptic flow at these energies, highlighting baryon-antibaryon differences and $ ext{phi}$ meson behavior at lower energies.

Findings

Significant baryon-antibaryon $v_2$ difference increases at lower energies.

$ ext{phi}$ meson $v_2$ is systematically lower at 11.5 GeV.

$v_2$ values are compared across RHIC and LHC energies.

Abstract

We present elliptic flow, $v_2$, measurements for charged and identified particles at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV at STAR. We compare the inclusive charged hadron $v_2$ to those from high energies at RHIC ($\sqrt{s_{NN}}$ = 62.4 and 200 GeV), at LHC ($\sqrt{s_{NN}}$ = 2.76 TeV). A significant difference in $v_2$ between baryons and anti-baryons is observed and the difference increases with decreasing beam energy. We observed the $v_2$ of $\phi$ meson is systematically lower than other particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 11.5 GeV.