The rarefaction of oblate shaped nuclear matter in heavy-ion collisions

Abstract We examine the disintegration stage of a hot zone in a high energy heavy-ion collision using hydrodynamics. We consider the initial non-homogeneously compressed matter to have an oblate shape. An approximate solution to the hydrodynamic equations is obtained by solving two coupled non-linear differential equations for the semiaxes of the boundary. We show that the boundary passes through a spherical shape and finally ends in a prolate configuration as the rarefaction proceeds. We apply the model to heavy-ion reactions to calculate angular distributions. We compare our theoretical results with experiments selected for central collision for the reaction C + Ag and O + Ag at energies about 200 MeV/nucleon. Good agreement between theory and experiment is obtained. Comparison with experiment allows estimating the ratio between the major and minor axis of the original oblate shape. It is shown that both non-homogeneity and shape asymmetry lead to enhanced forward and backward ejection of matter in the c.m. frame.