Light Nuclei Collectivity from $\sqrt{s_{\rm NN}}$ = 3 GeV Au+Au Collisions at RHIC

TL;DR

This study measures azimuthal anisotropy of light nuclei in 3 GeV Au+Au collisions, revealing baryonic dominance and unique flow behaviors at low energies, contrasting higher-energy phenomena.

Contribution

It provides the first detailed measurements of $v_1$ and $v_2$ for light nuclei at this energy, highlighting baryonic interactions' role in collective flow.

Findings

Atomic mass number scaling in $v_1$ slopes at mid-rapidity.

Negative $v_2$ values at mid-rapidity for all light nuclei.

Model calculations agree with observed baryonic dominance.

Abstract

In high-energy heavy-ion collisions, partonic collectivity is evidenced by the constituent quark number scaling of elliptic flow anisotropy for identified hadrons. A breaking of this scaling and dominance of baryonic interactions is found for identified hadron collective flow measurements in $\sqrt{s_{\rm NN}}$ = 3 GeV Au+Au collisions. In this paper, we report measurements of the first- and second-order azimuthal anisotropic parameters, $v_1$ and $v_2$, of light nuclei ($d$, $t$, $^{3}$He, $^{4}$He) produced in $\sqrt{s_{\rm NN}}$ = 3 GeV Au+Au collisions at the STAR experiment. An atomic mass number scaling is found in the measured $v_1$ slopes of light nuclei at mid-rapidity. For the measured $v_2$ magnitude, a strong rapidity dependence is observed. Unlike $v_2$ at higher collision energies, the $v_2$ values at mid-rapidity for all light nuclei are negative and no scaling is observed with the atomic mass number. Calculations by the Jet AA Microscopic Transport Model (JAM), with baryonic mean-field plus nucleon coalescence, are in good agreement with our observations, implying baryonic interactions dominate the collective dynamics in 3 GeV Au+Au collisions at RHIC.