# Bulk Properties of the Medium Produced in Relativistic Heavy-Ion Collisions from the Beam Energy Scan Program

## TL;DR

This paper reports systematic measurements of bulk properties of matter produced in gold-gold collisions at various energies, revealing insights into the chemical and kinetic freeze-out conditions across a broad energy range at RHIC.

## Contribution

It provides new systematic data on bulk properties and freeze-out dynamics in heavy-ion collisions over a wide energy spectrum at RHIC.

## Key findings

- Particle yields and ratios vary with collision energy and centrality.
- Freeze-out parameters show energy dependence, indicating changing chemical and kinetic conditions.
- Results help map the QCD phase diagram at different baryon chemical potentials.

## Abstract

We present measurements of bulk properties of the matter produced in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons ($\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity ($|y|<$0.1) results for multiplicity densities $dN/dy$, average transverse momenta $\langle p_T \rangle$ and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.