Time Evolution of Fast Particles During the Decay of Hadronic Systems
  A phenomenological model is presented based on the formation of nuclear thermodynamic system during the collision of heavy ions in the regime of intermediate and high energy regions. The formulation and the dynamic picture are determined by solving the Vlasov equation. The solution is dressed in the form of a power series. The first term of which is the equilibrium distribution in phase space. The rest, are time dependent perturbation terms due to the multiple strong interactions inside the system. The temperature gradient and the derivatives of the phase function are calculated. The time dependence of the angular emission of the produced particles is studied. It is found that particles emitted in the forward direction are produced in the early stage of the reaction, far from the equilibrium. Backward production comes in a later stage when the system constituents undergo multiple cascade collisions. 
Mohamed Tarek Hussein, Nabila Mohamed Hassan and Naglaa El-Harby