Hadronic Matter at High  Hot and Dense Nuclear  Status and Highlights

How to Proceed

Summarising, the physics of hot and dense hadronic matter has received a large boost especially with the complement of detectors now operating at the SIS facility of GSI. The quest for the nuclear matter equation of state and more generally the search for the properties of extended nuclear matter has entered a new domain. Precursor phenomena of chiral symmetry restoration could be at work and would offer an exciting view on the generation of masses in strongly interacting systems. Especially the density dependence can be studied with intermediate energy heavy ion reactions in a very clean way at moderate temperatures. Whether the fundamental chiral symmetry provides the basis for a consistent description of the multitude of new data needs to be explored with high priority. With a more solid understanding of the ingredients many of the current ambiguities in the theoretical description of the data and the modelling of the reaction could vanish. The top priorities of this research program are:

 
• Vigorous pursuit of the ongoing experimental program including the measurements with the heaviest beams and the full energy that are already anticipated for the near future. These should aim at a complete set of data on hadronic observables including an excitation function and system size dependence of all flow phenomena and of particle production.
• This information should be complemented by electromagnetic

probes and thus the timely completion of the high resolution dilepton spectrometer HADES, allowing for an independent more direct view on medium effects possibly induced by chiral symmetry restoration.
• Making use of the complement of detectors existing or under construction, the SIS program would benefit, even without major new detectors, from a moderate upgrade in beam energy thus elucidating the transition region between Bevalac and SIS energies on the one hand and the AGS energy regime on the other hand. It may be in this intermediate region that the phase boundary to quark matter is first reached and experimental observables that could signal this have been proposed.