Interpretation of the first data on central Au+Au collisions ats=56Aand130AGeV

We compare three semimicroscopic theories to the first data on particle production in central Au+Au collisions taken at RHIC by the PHOBOS Collaboration as well as to existing data on central Pb+Pb collisions taken at the SPS by the NA49 Collaboration. The Linear Extrapolation of Ultrarelativistic nucleon-nucleon Scattering to nucleus-nucleus collisions (LEXUS) represents the SPS data quite well but predicts too many particles at RHIC. The wounded nucleon model predicts too few particles at both the SPS and RHIC; the collective tube model predicts fewer particles still. This suggests a transition in the dynamics of particle production between $\sqrt{s}=17\mathrm{}$ and $56A\hspace{0.5em}\mathrm{GeV}$ as one goes from the SPS to RHIC.