Longitudinal expansion of matter formed by partial stopping in relativistic heavy ion collisions

Abstract

We investigate the modification of Landau's solution of hydrodynamic expansion of a fireball formed in relativistic heavy ion collisions when there is partial transparency. In our model of collision we assume that the transparent fraction (of nuclei) creates a color flux tube behind it which eventually produces QCD matter (t-fluid) outside the central QCD matter (s-fluid) formed by stopped nuclei. Thus the s-fluid expands against the nonzero pressure due to the t-fluid when the transparency is small. It makes the boundary condition on the expanding side of the s-fluid different from that of Landau and hence leads to a new solution of the hydrodynamic equations. Using the new solution we calculate the particle multiplicity distribution which is different from that of Landau, and the modification depends on the fraction of stopping.