9509266 Ko In nucleus-nucleus collisions at relativistic velocities, a piece of matter with temperature and density similar to that in the early universe after the Big Bang and the interior of neutron stars can be created. In this proposal, we shall investigate the properties of this hot dense matter using both effective Lagrangians and models that are based on the quantum chrodynamics. In particular, hadron masses and couplings at finite densities and temperatures will be studied since they are expected to be significantly modified in a medium. Including these medium effects in the relativistic transport model allows a realistic description of heavy ion collisions at energies available from present accelerators. The study of dilepton production from these collisions will then provide direct information on the properties of the hot dense matter due to the relatively weak interactions of dileptons in matter. The production of strange particles will also be investigated as they offer another promising probe of the hot dense matter as a result of strangeness conservation. Our long range goal is to extend the relativistic transport model to include the quark and gluon degrees of freedom so that one can describe nuclear collisions at future relativistic heavy ion colliders in which a quark-gluon plasma is expected to be formed in the initial stage. the proposed study makes it possible to identify the existence of the quark-gluon plasma and to study its properties. ***
