Hydrodynamics at large baryon densities: Understanding proton vs. anti-proton v_2 and other puzzles

TL;DR

This paper investigates how initial state conditions, baryon stopping, and baryon transport influence the evolution of heavy ion collisions, explaining observed differences in proton and anti-proton flow and other experimental puzzles.

Contribution

It introduces a hybrid model combining hydrodynamics and transport methods to better understand baryon dynamics at various collision energies.

Findings

Reproduces experimental data on particle flow and freeze-out parameters.

Highlights the importance of baryon-number current propagation.

Shows non-monotonic behavior of effective slope parameters with particle mass.

Abstract

We study the importance of the initial state, baryon stopping and baryon number transport for the dynamical evolution of a strongly interacting system produced in heavy ion collisions. We employ a hybrid model, which combines the fluid dynamical evolution of the fireball with a transport treatment for the initial state and the final hadronic phase. We present results for collisions at beam energies from sqrt{s_{NN}}=7.7 to 200 GeV. We study various observables such as the centrality dependent freeze out parameters, the non-monotonic behavior of effective slope parameter parameter with particle mass as well as the apparent difference in particle and anti-particle elliptic flow. Our results are in reasonable agreement with the available data. We find that the propagation of the baryon-number current in the hydrodynamic evolution as well as the transport treatment of the hadronic phase are essential for reproducing the experimental data.