Results from the STAR Beam Energy Scan Program

TL;DR

This paper reports on the STAR experiment's results from the RHIC beam energy scan, exploring QCD phase diagram features through various collision energies, analyzing particle spectra, flow, and fluctuations to search for the critical point.

Contribution

It provides new experimental data on particle production, flow, and fluctuations at multiple energies, advancing the search for the QCD critical point and phase boundary.

Findings

Particle spectra and yields at 7.7 GeV are presented.

Flow measurements ($v_1$, $v_2$) at 7.7, 11.5, and 39 GeV are reported.

Event-by-event fluctuation results at 39 GeV are shown.

Abstract

The main aim of the beam energy scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC) is to explore the quantum chromodynamics (QCD) phase diagram. The specific physics goal is to search for the phase boundary and the QCD critical point. We present results from Au+Au collisions at various energies collected in the BES program by the Solenoidal Tracker At RHIC (STAR) experiment. First results on transverse momentum ($p_{T}$) spectra, $dN/dy$, and average transverse mass ($< m_{T} >$) for identified hadrons produced at mid-rapidity for $\sqrt{s_{NN}}$ = 7.7 GeV are presented. Centrality dependence of $dN/dy$ and $< p_{T} >$ are also discussed and compared to corresponding data from other energies. In addition, first results on charged hadron directed ($v_{1}$) and elliptic flow ($v_{2}$) for $\sqrt{s_{NN}}=$ 7.7, 11.5, and 39 GeV are presented. New results on event-by-event fluctuations (particle ratio, net-proton and net-charge higher moments) are presented for $\sqrt{s_{NN}}=$ 39 GeV.