Joseph Kapusta (Minnesota, USA)

Many theoretical models predict a first order phase transition between hadrons and quarks and gluons, ending in a critical point in the plane of temperature versus baryon chemical potential. At the present time, lattice QCD calculations are not able to confirm or deny that. Ultimately, physics is an experimental science. I will briefly review what has been learned at various heavy ion accelerators, and how challenging it is for theoretical calculations to address the issue.