Indications for a Critical End Point in the Phase Diagram for Hot and Dense Nuclear Matter

Excitation functions for the Gaussian emission source radii difference (Rout2-Rside2) obtained from two-pion interferometry measurements in Au+Au (sNN=7.7-200 GeV) and Pb+Pb (sNN=2.76 TeV) collisions are studied for a broad range of collision centralities. The observed nonmonotonic excitation functions validate the finite-size scaling patterns expected for the deconfinement phase transition and the critical end point (CEP), in the temperature versus baryon chemical potential (T,μB) plane of the nuclear matter phase diagram. A finite-size scaling (FSS) analysis of these data suggests a second order phase transition with the estimates Tcep∼165 MeV and μBcep∼95 MeV for the location of the critical end point. The critical exponents (ν≈0.66 and γ≈1.2) extracted via the same FSS analysis place this CEP in the 3D Ising model universality class.