Study on chemical equilibrium in nucleus-nucleus collisions at   relativistic energies
  We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the chemical equilibration of the system as a function of center of mass energy and of the parameters of the source. Additionally, we have tested and compared different versions of the statistical model, with special emphasis on possible explanations of the observed strangeness hadronic phase space under-saturation. 
Jaakko Manninen, Francesco Becattini, Antti Keranen, Marek Gazdzicki   and Reinhard Stock