Cold compression of nuclei induced by antiprotons
On the basis of a dynamical Relativistic Mean Field (RMF) model we study the response of a nucleus on an antiproton implanted in its interior. We solve the Vlasov equation for the p̄-nuclear system assuming different strengths of attractive p̄ potential and show that a compressed state is formed on a rather short time scale of about 4 ÷ 10 fm/c. The evolution of the system after p̄ annihilation is simulated using the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model. Finally, several observables sensitive to the p̄ annihilation in a compressed nuclear configuration are proposed, e.g. the nucleon kinetic energy spectra and the total invariant mass distributions of produced mesons.
Analysis of subthreshold antiproton production in p-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 [rho][gt][rho][sub 0] we examine the differential antiproton spectra as a function of the antiproton self-energy. A detailed comparison with the available experimental data for [ital p]-nucleus and nucleus-nucleus reactions shows that the antiproton feels a moderately attractive mean field at normal nuclear matter density [rho][sub 0] which is in line with a dispersive potential extracted from the free annihilation cross section.
Quantum fluctuation effects on nuclear fragment formation
Multifragmentation in Au+Au collisions is investigated at incident energies in the range 100-400 MeV per nucleon by means of a recently developed quantal Langevin model. The inclusion of quantum fluctuations enhances the average multiplicity of intermediate mass fragments, especially in central collisions. This is mainly because the excitation energies of fragments are reduced due to the quantal behavior of intrinsic specific heat.