Analysis of charged hadron multiplicity distributions at RHIC

It is demonstrated that with Heinz＇s collective flow model charged particle distributions at AGS and lower SPS energies （less than 20 GeV/n） , can successfully be analyzed, but that the model fails for the RHIC data. Heinz＇s model calculation underestimates the tails of the charged particle distributions from RHIC, the discrepancy becoming bigger as the energy increases. To study the multiplicity distributions at RHIC we develop the so-called ＂Thermalization Component Model＂, which is based on Heinz＇s collective flow model. It is realized that the limitation of phase space of collective flow can be reflected in that of the thermalization region. By comparing the contributions of particle production from the thermaUzation regions at different energies and different centralities, we can deepen our understanding of the features of collective motion at RHIC.