Evidence for a Soft Nuclear Equation-of-State from Kaon Production in   Heavy Ion Collisions
  The production of pions and kaons has been measured in Au+Au collisions at beam energies from 0.6 to 1.5 AGeV with the Kaon Spectrometer at SIS/GSI. The K+ meson multiplicity per nucleon is enhanced in Au+Au collisions by factors up to 6 relative to C+C reactions whereas the corresponding pion ratio is reduced. The ratio of the K+ meson excitation functions for Au+Au and C+C collisions increases with decreasing beam energy. This behavior is expected for a soft nuclear equation-of-state. 
C. Sturm, I. Boettcher, M. Debowski, A. Foerster, E. Grosse, P.   Koczon, B. Kohlmeyer, F. Laue, M. Mang, L. Naumann, H. Oes...