The Statistical Model, assuming chemical equilibrium and local strangeness conservation, describes most of the observed features of strange particle production from SIS up to RHIC. The calculated smooth increase of the K-/pi- ratio and the shape of the Xi-/pi+ and Omega-/pi+ ratios, exhibiting maxima at different incident energies, are consistent with the presently available experimental data.
Deviations are observed in the recently discovered sharp peak in the K+/pi+ ratio around 30 A GeV. Just at this incident energy, a change from the freeze-out condition occurs. At lower energies baryons dominate, while above this energy mesons dominate the freeze-out.
Furthermore, at higher energies, chemical and thermal freeze-out seem to be separated while below they coincide. HBT studies indicate that the extracted volumina pass a minimum around 30 A GeV. All these changes could influence the freeze-out dynamics, and deviations from the usual freeze-out curve might happen. This affects only some particle ratios and others not.