Elliptic flow of light nuclei in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

TL;DR

This paper measures the elliptic flow of light nuclei in gold-gold collisions at high energy, showing mass number scaling and consistency with quark number scaling, indicating partonic collectivity in the collision dynamics.

Contribution

It provides the first detailed measurement of light nuclei elliptic flow at RHIC and demonstrates their scaling behaviors, supporting models of partonic collectivity and coalescence.

Findings

Light nuclei $v_{2}$ follows atomic mass number scaling.

Scaled $v_{2}$ aligns with NCQ scaling for baryons and mesons.

Evidence of partonic collectivity in transverse expansion dynamics.

Abstract

We present the elliptic flow ($v_{2}$) of light nuclei at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The results are measured in the STAR experiment at RHIC. The $v_{2}$ measurement for light nuclei as a function of transverse momentum $p_{T}$ is found to follow an approximate atomic mass number ($A$) scaling. We compare the measured nuclei $v_{2}$ to results from a dynamical coalescence model calculation. The $v_{2}$ values for light nuclei are further scaled to the number of constituent quarks (NCQ) of their constituent nucleons and are consistent with NCQ scaled $v_{2}$ for baryons and mesons. The dominance of partonic collectivity in the transverse expansion dynamics in these collisions naturally produces such a consistent picture. Similar to other hadrons, an increase of $p_{T}$-integrated $v_{2}$ scaled by the participant eccentricity as a function of collision centrality has been observed.