Chemical freeze-out of strange particles and possible root of strangeness suppression

Two approaches to treat the chemical freeze-out of strange particles in the hadron resonance gas model are analyzed. The first one employs their non-equillibration via the usual gamma(s) factor and such a model describes the hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and RHIC energies with chi(2)/dof similar or equal to 1.15. Surprisingly, at low energies we find not the strangeness suppression, but its enhancement. Also we suggest an alternative approach to treat the strange particle freeze-out separately, but with the full chemical equilibration. This approach is based on the conservation laws which allow us to connect the freeze-outs of strange and non-strange hadrons. Within the suggested approach the same set of hadron multiplicities can be described better than within the conventional approach with chi(2)/dof similar or equal to 1.06. Copyright (C) EPLA, 2013