Non-equilibrium and residual memory in momentum space of fragmenting sources in central heavy-ion collisions

Abstract

The non-equilibrium in momentum space of fragmenting sources in central heavy-ion collisions at Fermi energy is reproduced by partly compensating for the fermionic feature in the isospin-dependent quantum molecular dynamics model. A memory loss ratio is defined to investigate the degree of entrance channel memory loss. The incomplete memory loss and the linear correlation between the memory loss ratio and the normalized radial flow energy are found both from experimental data and calculations. The residual memory indicates that the global equilibrium is not achieved in central collisions. The local equilibrium is achieved only in a very small central region of the fragmenting source. Both the asymmetry distribution of the expansive flow and the deformation of the fragmenting source are the consequences of the residual memory. A method to extract the transversal-to-longitudinal axis ratio of the expanding fragmenting source is suggested.