Heavy Ion Tea

Explore the X-Fluid at RHIC
Jinfeng Liao (LBNL)

Abstract: In this talk I will discuss several aspects of the QCD partonic fluid, which I call X-fluid, found at RHIC. (i) It will be shown that a non-collective component, different from the usual collective hydrodynamic component, contributes to the measured elliptic flow v2 and becomes dominant with increasing pT: this has big impact on extracting viscosity from v2 and on whether the X-fluid is more like ideal or viscous fluid. (ii) A critical examination on the "perfect fluid" claim reveals its faulty side. In particular the misconception in comparing RHIC fluid to normal non-relativistic fluid is pointed out and a quality measure for fluidity proposed, according to which the X-fluid may be just as good as water. The relevance of supercritical fluid to RHIC is discussed. (iii) Finally the interpretation of the microscopic dynamics of the X-fluid will be connected to the big picture of QCD confinement problem, and it will be argued that the X-fluid may actually be a MAGNETIC fluid. Related theoretical and experimental issues will also be discussed.