Transverse Hydrodynamics with Sudden Izotropization and Freeze-Out

We assume that the early evolution of matter produced in relativistic heavy-ion collisions is described by the transverse hydrodynamics. In this approach only transverse degrees of freedom are thermalized, while the longitudinal motion is described by free streaming. When the energy density of the system drops to a certain value, the system becomes isotropic (locally, in the momentum space) and freezes out. The sudden isotropization transition is described with the help of the Landau matching conditions, and the freeze-out is modeled with Therminator. Within this scenario one is able to reproduce in the quite satisfactory way the transverse-momentum spectra, the elliptic flow coefficient v2, and the HBT radii of pions studied at RHIC (Au + Au collisions at √sNN = 200 GeV). The obtained results indicate that the system produced at RHIC does not have to be fully thermalized in the early stage. On the other hand, the final three-dimensional thermalization is necessary to reproduce the HBT radius Rlong. (authors)