Modeling relativistic heavy ion collisions: From AGS to SPS

Abstract

The importance of hadronic resonances in relativistic heavy ion collisions, from AGS to SPS energies, is now widely recognized. The systematics from Si beams to Au beams, provide overwhelming evidence that the hadronic resonance description of the heavy ion collisions is quite accurate at AGS energies with the possible exception when the highest baryon densities are reached. The authors have seen the importance of resonance rescattering in nucleus-nucleus collisions. However, they have very little direct knowledge on the cross-sections and the rescattering mechanisms of these resonances. They also have the formation of high baryon density regions, but they have no direct knowledge on the medium dependence of the hadronic cross sections involved. In the hadronic cascade model, ARC, they have assumed that baryon resonances rescatter as nucleons and the meson resonances as pions, and the free space cross-sections for nucleons and pions are used through out the collisions. It would be much better if these assumptions could be verified independently through experiments. For details of resonance rescattering, they obtain some information by reconstructing the resonances from the observed hadrons. Determining the hadronic cross sections in a dense medium is a hard problem. The authors describe tests on the sensitivities ofmore » medium dependence to the observed spectra. These tests make very drastic and unrealistic assumptions on the density dependence of the hadronic cross sections, but as sensitivity tests they are nevertheless quite revealing.« less