Non-local kinetic simulation of heavy ion collisions

Abstract

The numerical solutions of nonlocal and local Boltzmann kinetic equations for the simulation of peripheral and central heavy ion reactions are compared. The experimental finding of enhancement of mid-rapidity matter shows the necessity to include nonlocal corrections. While the in-medium cross section changes the number of collisions and not the transferred energy, the nonlocal scenario changes the energy transferred during collisions. The renormalisation of quasiparticle energies by using the Pauli-rejected collisions leads to a further enhancement of mid-rapidity matter distribution and is accompanied by a dynamical softening of the equation of state. The simulation results are parameterised in terms of time dependent thermodynamical variables in the Fermi liquid sense. This allows one to discuss dynamical trajectories in phase space. A combination of thermodynamical observables is constructed which locates instabilities and points of possible phase transition under iso-nothing conditions. Two different mechanisms of instability, a short time surface-dominated instability and later a spinodal-dominated volume instability is found. The latter one occurs only if the incident energies do not exceed significantly the Fermi energy and might be attributed to spinodal decomposition.