Outlook

Abstract

The heavy ion research described in these reviews focussed predominantly on collision energies around the nuclear Coulomb threshold. To put this energy in perspective one could say that the relative velocity of two nuclei impinging on each other is small compared to the so-called Fermi velocity at which individual nucleons move inside the nucleus. As a consequence nuclear matter tends to be in or close to thermal equilibrium at all times during the nuclear collisions because the energy is quickly dissipated inside the nucleus through moving nucleons. However, one may anticipate a change in this situation if the energy of the heavy ion beams increases further. Then a nucleus smashing into another nucleus may cause shock waves or the same phenomena which are observed if an airplane exceeds the speed of sound. Furthermore, nuclear compression and heating might be considerable. At even higher energies, the heavy ion exceeds many thresholds, like the one for the production of pions and other strange particles like lambda and sigma particle and even antiprotons. At the end of such a process the nuclear liquid may be compressed and heated so much that nucleons with their three quarks in a bag lose their individuality, quark are deconfined and form an extended bag of many quarks and gluons, according to today's knowledge of the ultimate constituents of matter. And even the atomic physics may b taken to the extreme by depriving uranium atom of all electrons, leaving a tripped and naked uranium nucleus behind.