Free Streaming And Sudden Equilibration Approximation For The Early Stages Of Relativistic Heavy-Ion Collisions

Using a multi-phase transport (AMPT) model, we study the equilibration process of the early collision stages with free streaming and sudden equilibration approximation. In addition, the results of the transverse momentum spectra, the elliptic flow, the Hanbury-Brown twiss (HBT) parameters and the freeze-out eccentricity from the azimuthal angle dependence of the HBT radii are described within our approach. The results of the transverse momentum spectra and the elliptic flow are close to the experimental data. The HBT radii result is similar to that from the AMPT model. The eccentricity results indicate that the approximation leads to a slow drop of the eccentricity with increasing time. The slow decrease can be reflected in the freeze-out eccentricity obtained by HBT radii.