Beam Energy Dependence of First and Higher Order Flow Harmonics from the STAR Experiment at RHIC

TL;DR

This paper reports on STAR experiment measurements of flow harmonics across a range of collision energies, revealing complex energy-dependent behaviors in directed and triangular flow, with implications for understanding the quark-gluon plasma.

Contribution

It provides new measurements of flow harmonics from RHIC energies, highlighting the energy dependence of directed and higher-order flow components.

Findings

The $v_1$ slope for net protons changes sign twice at lower energies.

The beam energy dependence of $v_3$ was measured.

Flow harmonics $v_{1}$ to $v_{5}$ were characterized at 200 GeV.

Abstract

In these proceedings, we present STAR measurements of directed flow, $v_{1}$, for pions, protons and antiprotons between $\sqrt{s_{NN}} = 7.7$ GeV and 200 GeV. A striking observation is that the $v_1$ slope for net protons as a function of rapidity, $F = dv_1/dy$, which is an estimate of the directed flow contribution from baryon number transported to the midrapidity region, changes sign twice within the lower part of this energy range. We also present the measured beam energy dependence of triangular flow $v_{3}$, and the $n=1$ to $n=5$ flow harmonics for charged particles at 200 GeV.