Cluster-Flow and Resonance-Matter Formation in Ultrarelativistic Heavy-Ion Reactions

Abstract

One of the challenges of modern heavy ion physics is the extraction of the equation of state for extremely excited nuclear matter. In particular, the creation and study of hadron matter at high net baryon density has received much attention recently. Not much is known about the strenght of the mean fields at large baryon densities. It is expected that the momentum dependence of the nuclear forces1, the excitation into resonance matter2 and the phase transition into the QGP3 will playa crucial role for the created mean fields. In particular, QCD — as the accepted theory of strong interaction — contains chiral symmetry (in the limit of massless quarks) which is spontaneously broken in its groundstate, the QCD vacuum (see e.g. recent lattice calculations4). A rapid restoration of this symmetry with increasing baryon density is predicted by all approaches which embody this fundamental aspect of QCD5,6 Therefore, nucleus-nucleus collisions in the bombarding energy region of baryon stop- ping could be favorable in order to study such medium effects as compared to ultrahigh energies, for which the two colliding nuclei may become transparent to each other. Transport calculations based on hadronic excitations and rescattering like the RQMD approach (strings, resonances)7 or the ARC model (resonances)8 predict that beam energies between 10 to 15 AGeV — as studied experimentally at the BNL-AGS 9, 10, 11 — are well suited to create the desired high stopping and baryon densities.KeywordsNuclear MatterRapidity DistributionQuark MatterBaryon DensityCollective FlowThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.