Hadronic thermal model with distinct freeze-out temperature for baryons and mesons

Full text: In the last ten years a significant amount of experimental data for particle production in high energy heavy ion collisions have been accumulated in the energy range of 1 - 200 GeV at center of mass. These data are well described by thermal models in the approximation of global thermal equilibrium by considering only one global freeze-out temperature. However, it is important to call the attention to the different scales of meson and baryon thermal production thresholds, as well as to the differentiated cross section of the meson-meson and baryon-baryon processes. Therefore, there is no fundamental reason to assume that the mesonic and baryonic sectors of the system reach the equilibrium at the same time during the freeze-out process. Our purpose in the present work is to study how the usual results are changed within this alternative freeze-out scenario, with the separated meson and baryon freeze-out temperatures. However, as usual, only one baryonic potential for the whole system is considered. Thus we are dealing with three adjustable characteristic parameters to reproduce the experimental data. From the study of some nucleus-nucleus collisions a systematic is obtained for the values of the model parameters which can be used as a predictive instrument. (author)