On the chemical equilibration of strangeness-exchange reactions in heavy-ion collisions

The strangeness-exchange reaction π+Y↔K -+N is shown to be the dynamical origin of chemical saturation and equilibration for K - production in heavy-ion collisions up to beam energies of 10 AGeV. The hyperons occurring in this process are produced in association with K + in baryon-baryon and meson-baryon interactions. This connection is demonstrated by the ratio of K -/K + which does not vary with centrality and shows a linear correlation with the yield of pions per participant. At incident energies above AGS this correlation no longer holds due to the change in the production mechanism of kaons. © 2004 Elsevier B.V. All rights reserved.