Strange Particle Production from SIS up to Lhc

A review of strange particle production in heavy ion collisions at incident energies from SIS up to collider energies is presented. The differences between π, K⁺ and K^- production observed at low incident energies is discussed. Emphasis is given to the K⁺ production which gives an unique opportunity to extract information on the nuclear equation of state. A statistical model assuming chemical equilibrium and local strangeness conservation (i.e. strangeness conservation per collision) explains most of the observed features. The independence of the K⁺/K^- ratio on the number of participating nucleons observed between SIS and RHIC is consistent with this model. 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 μ_B.