Highlights from STAR heavy ion program

TL;DR

This paper reviews recent experimental findings from the STAR heavy-ion program at RHIC, focusing on quark-gluon matter properties, QCD phase diagram exploration, and signatures of topological and chiral effects in high-energy nuclear collisions.

Contribution

It provides a comprehensive overview of experimental results and future plans for probing the QCD phase diagram and topological properties in heavy-ion collisions at RHIC.

Findings

Evidence of collective behavior of heavy quarks in nucleus-nucleus interactions

Constraints on energy loss models from jet and heavy hadron measurements

Observation of finite global vorticity indicating chiral effects

Abstract

Recent experimental results obtained in STAR experiment at the Relativistic heavy-ion collider (RHIC) with ion beams will be discussed. Investigations of different nuclear collisions in some recent years focus on two main tasks, namely, detail study of quark-gluon matter properties and exploration of the quantum chromodynamics (QCD) phase diagram. Results at top RHIC energy show clearly the collective behavior of heavy quarks in nucleus-nucleus interactions. Jet and heavy hadron measurements lead to new constraints for energy loss models for various flavors. Heavy-ion collisions are unique tool for the study of topological properties of theory as well as the magneto-hydrodynamics of strongly interacting matter. Experimental results obtained for discrete QCD symmetries at finite temperatures confirm indirectly the topologically non-trivial structure of QCD vacuum. Finite global vorticity observed in non-central Au+Au collisions can be considered as important signature for presence of various chiral effects in sQGP. Most results obtained during stage I of the RHIC beam energy scan (BES) program show smooth behavior vs initial energy. However certain results suggest the transition in the domain of dominance of hadronic degrees of freedom at center-of-mass energies between 10--20 GeV. The stage II of the BES at RHIC will occur in 2019--2020 and will explore with precision measurements in the domain of the QCD phase diagram with high baryon densities. Future developments and more precise studies of features of QCD phase diagram in the framework of stage II of RHIC BES will be briefly discussed.