Chemical freeze-out curve in heavy-ion collisions and the QCD critical point

The chemical freeze-out curve in heavy-ion collisions is investigated in the context of QCD critical point (CP) search at finite baryon densities. Taking the hadron resonance gas picture at face value, chemical freeze-out points at a given baryochemical potential provide a lower bound on the possible temperature of the QCD CP. We first verify that the freeze-out data in heavy-ion collisions are well described by a constant energy per particle curve, E/N = const, under strangeness neutrality conditions (μS ≠ 0, μQ ≠ 0). We then evaluate the hypothetical freeze-out curve based on this criterion in the absence of strangeness neutrality (μS = 0, μQ = 0) and confront it with recent predictions on the CP location. We find that recent estimates based on Yang-Lee edge singularities from lattice QCD data on coarse lattices place the CP significantly below the freeze-out curve and are thus disfavored by the heavy-ion data. On the other hand, predictions based on functional methods and holography place the CP slightly above the freeze-out curve, indicating that the QCD CP may be located very close to the chemical freeze-out in A+A collisions at √sNN = 3.5 ÷ 5 GeV.