Strange Particle Production from SIS up to 40 A·GeV

A review of strange particle production in heavy ion collisions at incident energies from SIS up to 40 A·GeV is presented. A statistical model assuming chemical equilibrium and local strangeness conservation (i.e. strangeness conservation per collision) describes most of the observed features. It is demonstrated that the K- production at SIS energies occurs predominantly via strangeness exchange and that this channel is approaching chemical equilibrium. The observed maximum in the K+/π+ excitation function is also seen in the ratio of strange to non-strange particle production. The appearance of this maximum around 30 A·GeV is due to the energy dependence of the chemical freeze-out parameters temperature T and baryo-chemical potential μB.