Analysis of subthreshold antiproton production inp-nucleus and nucleus-nucleus collisions in the relativistic Boltzmann-Uehling-Uhlenbeck approach

We calculate the subthreshold production of antiprotons in the Lorentz-covariant relativistic Boltzmann-Uehling-Uhlenbeck (RBUU) approach employing a weighted testparticle method to treat the antiproton propagation and absorption nonperturbatively. We find that the antiproton differential cross sections are highly sensitive to the baryon and antiproton self-energies in the dense baryonic environment. Adopting the baryon scalar and vector self-energies from the empirical optical potential for proton-nucleus elastic scattering and from Dirac-Brueckner calculations at higher density ρ>${\mathrm{\rho }}_0$ we examine the differential antiproton spectra as a function of the antiproton self-energy. A detailed comparison with the available experimental data for p-nucleus and nucleus-nucleus reactions shows that the antiproton feels a moderately attractive mean field at normal nuclear matter density ${\mathrm{\rho }}_0$ which is in line with a dispersive potential extracted from the free annihilation cross section.