An explanation of the elliptic flow difference between proton and anti-proton from the UrQMD model with hadron potentials

TL;DR

This paper investigates the difference in elliptic flow between protons and anti-protons in heavy-ion collisions using the UrQMD model, highlighting the role of hadron potentials and early freeze-out in explaining experimental observations.

Contribution

It demonstrates that incorporating hadron potentials in the UrQMD model explains the observed flow difference between protons and anti-protons.

Findings

Anti-protons freeze out earlier with smaller v2 due to repulsive potentials.

Potential version of UrQMD reproduces experimental anti-proton v2 data.

Flow difference explained by early freeze-out and annihilation probabilities.

Abstract

The time evolution of both proton and anti-proton $v_2$ flows from Au+Au collisions at $\sqrt{s_{NN}}$=7.7 GeV are examined by using both pure cascade and mean-field potential versions of the UrQMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller $v_2$ values. Therefore, the experimental data of anti-proton $v_2$ as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.