Statistical model description of K+ and K- production between 1-10 A center dot GeV

The excitation functions of K+ and K- mesons in heavy ion collisions are st udied within a statistical model assuming chemical and thermal equilibrium with exact strangeness conservation. At low incident energies the associate production of kaons, i.e., the production of a K+ together with a hyperon and the production of a K- together with a K+, implies specific features: d ifferent threshold energies and different dependences of K+ and K- yields o n baryon number density. It is shown that the experimentally observed equal ity of the K+ and K- rates at energies root s - root s(th) less than or equ al to 0 is due to a crossing of the two excitation functions. Furthermore, the independence of the K+ to K- ratio on the number of participating nucle ons observed at 1 and 10 A.GeV is consistent with this model. (C) 2000 Publ ished by Elsevier Science B.V.