On the Role of Dissipation in the Early Stages of Relativistic Heavy Ion Collisions

The influence of the dissipative terms on the conditions of formation and the characteristic parameters of shock waves in relativistic nuclear collisions is investigated for three types of equation of state (non linear QHD-1, resonance gas and lattice QCD). Energy and velocity profiles are obtained in a one-dimensional model; the duration of the shock phase and width of the shock front are calculated. It is shown that the presence of a phase transition results in a strong enhancement of the width of the shock front, which results in an increase of transparency. This effect, combined with the fact that the nuclei have a finite size, prevents the energy density to rise to its maximum value (full stopping) as would be predicted by a non dissipative shock model.