Exploring the QCD phase diagram at finite baryon density and searching for the QCD critical point remain major goals of nuclear physics. I will first discuss recent constraints obtained from the constant entropy contours method, recently extended to a four-dimensional thermodynamic parameter space. These results place the candidate critical region near the chemical freeze-out in intermediate-energy heavy-ion collisions. I will then present an extended hydrodynamic framework for describing proton-number cumulants in heavy-ion collisions. Augmented with a maximum-entropy freeze-out prescription and a generalized subensemble acceptance method, the framework relates experimentally measured proton cumulants to equilibrium baryon-number susceptibilities while consistently incorporating the equation of state, kinematic acceptance, and global baryon number conservation. A Bayesian analysis of experimental fluctuation measurements then enables the direct extraction of baryon-number susceptibilities from heavy-ion collision data. I will discuss the inferred susceptibilities in comparison with a lattice-QCD-based equation of state and examine their implications for the possible existence and location of the QCD critical point.
Talk given by Volodymyr Y. Vovchenko (University of Houston) at the Hadron Ion Tea (HIT) Seminar Series at Lawrence Berkeley National Laboratory.
Host: Volker Koch