DOES THE REDUCTION OF THE MASS IN THE MEDIUM ENHANCE THE PRODUCTION OF ANTIPROTONS IN HIGH-ENERGY NUCLEAR-REACTIONS

We investigate the role of medium effects on the production of antipro tons in nucleus-nucleus collisions at subthreshold energies. The react ion dynamics is simulated within the framework of quantum molecular dy namics. The antiprotons, produced through elementary baryon-baryon pro cesses, are propagated in its time-dependent self-consistent mean fiel d. Both absorption and rescattering by the baryonic environment are ev aluated dynamically. The density and temperature dependence of the ass ociated scalar and vector self-energies are calculated on the basis of an effective Nambu-Jona-Lasinio model. We found that the inclusion of the self-energies enhances the production of antiprotons. The calcula ted spectra are in good agreement with the experimental data and consi stent with the formation of a very hot phase from which antiprotons ar e produced.