Calculating QCD Phase Diagram Trajectories of Nuclear Collisions using a Semi-analytical Model

TL;DR

This paper introduces a semi-analytical model to calculate the trajectories of nuclear collisions in the QCD phase diagram, accounting for finite nuclear thickness effects at low to moderate energies, and compares results with lattice QCD and experimental data.

Contribution

The paper presents a semi-analytical model that incorporates finite nuclear thickness effects to determine QCD phase diagram trajectories in heavy ion collisions.

Findings

Finite nuclear thickness significantly influences energy and charge densities.

Trajectories differ when using ideal gas versus lattice QCD equations of state.

Transverse flow impacts the evolution trajectories in the phase diagram.

Abstract

At low to moderate collision energies where the parton formation time $\tau_F$ is not small compared to the nuclear crossing time, the finite nuclear thickness significantly affects the energy density $\epsilon(t)$ and net conserved-charge densities such as the net-baryon density $n_B(t)$ produced in heavy ion collisions. As a result, at low to moderate energies the trajectory in the QCD phase diagram is also affected by the finite nuclear thickness. Here, we first discuss our semi-analytical model and its results on $\epsilon(t)$, $n_B(t)$, $n_Q(t)$, and $n_S(t)$ in central Au+Au collisions. We then compare the $T(t)$, $\mu_B(t)$, $\mu_Q(t)$, and $\mu_S(t)$ extracted with the ideal gas equation of state (EoS) with quantum statistics to those extracted with a lattice QCD-based EoS. We also compare the $T-\mu_B$ trajectories with the RHIC chemical freezeout data. Finally, we discuss the effect of transverse flow on the trajectories.