Highlights of the Beam Energy Scan from STAR

TL;DR

This paper reviews the initial results from the STAR experiment's beam energy scan at RHIC, highlighting agreements and discrepancies with previous data, and presenting new observations on freeze-out parameters and flow differences across energies.

Contribution

It provides the first STAR results from the BES program, including new insights into chemical freeze-out and flow behavior at different energies.

Findings

Particle yields agree with SPS and AGS data

Azimuthal HBT and fluctuation results differ at some energies

Centrality dependence of freeze-out parameters observed

Abstract

The first part of the beam energy scan (BES) program at RHIC was successfully completed in the years 2010 and 2011. First STAR results from particle yield measurements are in good agreement with previously published data from SPS and AGS experiments whereas other results like azimuthal HBT and $K/\pi$ event-by-event fluctuations differ at some energies. In addition, new observations like the centrality dependence of chemical freeze-out parameters ($T_{\rm{ch}}$ and $\mu_{B}$) or the smoothly increasing difference with decreasing energy in the elliptic flow $v_{2}$ between particles and corresponding anti-particles, are discussed.