Excitation function of entropy and pion production from AGS to SPS   energies
  Entropy production in the initial compression stage of relativistic heavy-ion collisions from AGS to SPS energies is calculated within a three-fluid hydrodynamical model. The entropy per participating net baryon is found to increase smoothly and does not exhibit a jump or a plateau as in the 1-dimensional one-fluid shock model. Therefore, the excess of pions per participating net baryon in nucleus-nucleus collisions as compared to proton-proton reactions also increases smoothly with beam energy. 
M. Reiter, A. Dumitru, J. Brachmann, J.A. Maruhn, H. St\"ocker, W.   Greiner