Energy Dependence of Directed Flow in Au+Au Collisions from a Multi-phase Transport Model

TL;DR

This study uses a multi-phase transport model to analyze the energy dependence of directed flow in gold-gold collisions across various energies, providing insights into early-time collective dynamics in heavy-ion collisions.

Contribution

It demonstrates the AMPT model's ability to reproduce the energy trend of directed flow and reveals a sign change in proton v1 slope at 130 GeV, highlighting features of anti-flow.

Findings

AMPT model reproduces v1(y) slope trend with energy.

Proton v1 slope changes sign at 130 GeV, indicating anti-flow.

Hadronic re-scattering has minimal effect on v1 at top RHIC energies.

Abstract

The directed flow of charged hadron and identified particles has been studied in the framework of a multi-phase transport (AMPT) model, for $^{197}$Au+$^{197}$Au collisions at $\sqrt{s_{NN}}=$200, 130, 62.4, 39, 17.2 and 9.2 GeV. The rapidity, centrality and energy dependence of directed flow for charged particles over a wide rapidity range are presented. AMPT model gives the correct $v_1(y)$ slope, as well as its trend as a function of energy, while it underestimates the magnitude. Within the AMPT model, the proton $v_1$ slope is found to change its sign when the energy increases to 130 GeV - a feature that is consistent with ``anti-flow''. Hadronic re-scattering is found having little effect on $v_1$ at top RHIC energies. These studies can help us to understand the collective dynamics at early times in relativistic heavy-ion collisions, and they can also be served as references for the RHIC Beam Energy Scan program.