Interplay of the emission from thermal and direct sources in relativistic heavy ion collisions

Abstract

The separation of the source created in ultrarelativistic heavy ion collisions into a thermalized dense core and an outer mantle consisting of independent nucleon-nucleon collisions is discussed. Indications for such a two-component picture are found in the transverse mass spectra of kaons, protons, and antiprotons produced in Au-Au collisions at $\sqrt{s}=200$ GeV. Estimates of the sizes of the thermal and direct sources are compared with models separating the interaction zone into a core and a corona. New initial conditions corresponding to the dense core lead to a stronger azimuthal asymmetry of the fireball, and pressure gradients also increase. We find faster transverse hydrodynamic expansion and stronger elliptic flow for the dense core initial conditions.