Pion entropy and phase-space densities in A+A collisions

We propose a method to estimate the entropy of thermal pions in A+A collisions irrespective of the unknown form of freeze-out (isothermal) hypersurface and transverse flows developed. We analyse the average phase-space densities and entropies of the thermal pions vs, their multiplicities and collision energies. The behaviour of these values apparently indicates the deconflnement and chiral phase transitions in relativistic nucleus-nucleus collisions.