Directed flow of transported and non-transported protons in Au+Au collisions from UrQMD model

TL;DR

This study uses the UrQMD model to analyze the directed flow of different proton groups in Au+Au collisions across various energies, explaining the sign change in flow without invoking phase transition effects.

Contribution

It provides a conventional explanation for the directed flow sign change by examining the interplay between transported and non-transported protons, challenging the idea that it solely indicates a phase transition.

Findings

Directed flow decreases with collision energy for sNN  11.5 GeV and above.

Sign change in proton flow can be explained by competing effects of different proton groups.

Differences in flow between protons and antiprotons are also explained.

Abstract

The directed flow of inclusive, transported and non-transported (including produced) protons, as well as antiprotons, has been studied in the framework of Ultra-Relativistic Quantum Molecular Dynamics approach (UrQMD model) for Au+Au collisions at\surdsNN =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. The rapidity, centrality and energy dependence of directed flow for various proton groups are presented. It is found that the integrated directed flow decreases monotonically as a function of collision energy for\surdsNN =11.5 GeV and beyond. However, the sign-change of directed flow of inclusive protons, seen in experimental data as a function of centrality and collision energy, can be explained by the competing effect of directed flow between transported and non-transported protons. Similarly the difference in directed flow between protons and antiprotons can be explained. Our study offers a conventional explanation on the cause of the v1 sign-change other than the antiflow component of protons alone which is argued to be linked to a phase transition.