Departamento de F́ısica, Universidade Federal de Santa Catarina

Attempts have been made to recreate conditions within the collision of heavy nuclei at ultra-relativistic energies, looking for signatures of the production of the QGP, which subsequently hadronizes [?]. Hadron multiplicities are observables which can provide valuable information on the nature of the medium from which they are produced. In this way, they are natural tools to look for QGP signatures. In order to model the data, the use of thermal models to describe hadronic collision spectra has been considered [?,?]. Studies including hadron-hadron dynamics in a sophisticated relativistic chiral SU(3) model, have shown that the hadron ratios obtained from SIS, AGS, SPS to RHIC hadron energies are also well described [?]. One would ask whether well known relativistic hadronic models [?,?] are able to successfully fit the mentioned chemical freeze-out hadronic ratios. In [?] it was shown that the new dynamics achieved by the models with density depend parameters makes the difference by having the best fits and that the mesons play an important role. By using a parametrization of the non-linear Walecka model which takes into account the binding energy of different hyperons, we present a study of particle production yields measured in central Au-Au collision at RHIC. Two sets of different hyperon-meson coupling constants are employed in obtaining the hadron production and chemical freeze-out parameters. These quantities show a weak dependence on the used hyperon-meson couplings. Results are in good overall accordance with experimental data. We have found that the repulsion among th