  Two-pion interferometry measurements are studied for a broad range of
collision centralities in Au+Au (Root_s = 7.7 - 200 GeV) and Pb+Pb (Root_s =
2.76 TeV) collisions. They indicate non-monotonic excitation functions for the
Gaussian emission source radii difference [(R_out)^2 - (R_side)^2], suggestive
of reaction trajectories which spend a fair amount of time near a "soft point"
in the equation of state (EOS) that coincides with the critical end point
(CEP). A Finite-Size Scaling (FSS) analysis of these excitation functions,
provides further validation tests for the CEP. It also indicates a second order
phase transition at the CEP, and the values T^{cep} ~ 165 MeV and mu_B^{cep} ~
95 MeV for its location in the (T, mu_B)-plane of the phase diagram. The static
critical exponents (nu ~ 0.66 and gamma ~ 1.2) extracted via the same FSS
analysis, place this CEP in the 3D Ising model universality class. A Dynamic
Finite-Size Scaling analysis of the excitation functions, gives the estimate z
~ 0.87 for the dynamic critical exponent, suggesting that the associated
critical expansion dynamics is dominated by the hydrodynamic sound mode.
