Composite particles and entropy production in relativistic nuclear collisions

The particle production (p,d,t${,}^3$He${,}^4$He) was studied for 400 and 650 MeV/nucleon Nb+Nb and 400 and 1050 MeV/nucleon Ca+Ca. The chemical freeze-out density of the participants and the entropy produced were deduced for each system. The chemical freeze-out densities are close to normal nuclear density. The entropy production extrapolated for infinite nuclear matter is independent of target-projectile combination at 400 MeV/nucleon and changes little with increasing bombarding energy, but the absolute values are strongly model dependent. The low entropy, when compared to fireball calculations, indicates that compression is present in the collisions. Therefore entropy values in principle can help in the determination of the equation of state for nuclear matter.