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 antiprotons in nucleus-nucleus collisions at subthreshold energies. The reaction dynamics is simulated within the framework of quantum molecular dynamics. The antiprotons, produced through elementary baryon-baryon processes, are propagated in its time dependent self-consistent mean field. Both absorption and rescattering by the baryonic environment are evaluated dynamically. The density and temperature dependence of the associated 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 calculated spectra are in good agreement with the experimental data and consistent with the formation of a very hot phase from which antiprotons are produced. (Author)