What determines the K- multiplicity at energies around (1-2)A GeV?

In heavy ion reactions at energies around (1-2)A GeV the measured K- yields appear rather high as compared to pp collisions as shown by the KaoS Collaboration. Employing quantum molecular dynamics simulations, we show that this is caused by the fact that the dominant production channel is not BB→BBK+K- but the mesonic Λ(Σ)π→K-B reaction. Because the Λ (Σ) stem from the reaction BB→Λ(Σ)K+B, the K+ and the K- yield are strongly correlated, i.e., the K-/K+ ratio occurs to be nearly independent of the impact parameter as found experimentally. The final K- yield is strongly influenced by the K+N [due to their production via the Λ(Σ)] but very little by the K-N potential