Study of the QCD phase structure at HIAF

Abstract

High-energy nuclear collisions offer a unique opportunity for studying the properties of the nuclear matter under extreme conditions, the evolution of the universe soon after the big bang as well as the inner structure of stars. Quantum chromodynamics (QCD), the theory for strong interaction, has predicted the existence of the new form of matter, where the de-confined quarks and gluons move “freely” in a volume that is much larger than that of an ordinary nucleon, the quark-gluon plasma (QGP). After more than thirty years of searching, scientists have collected circumstantial evidences of QGP from the relativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Thermodynamically one might expect phase boundary or/and critical point that accompany the new phase of matter. Nowadays the QCD phase structure, especially in the high baryon density region, has become the focus in order to search for the QCD phase boundary and possible critical point. In this article, the experimental status on the QCD phase structure will be reviewed. Discussion will include the collectivity, chirality and criticality in high-energy nuclear collisions. These will be followed by the discussion of the main physics programs for the future experiment. The CSR-External-target Experiment (CEE) at both HIRFL and HIAF accelerator complexes, will be discussed.