The Simulation Study Of Anisotropic Flow At Sub-GeV Energy

Sub-Ge V energy region is of great importance for people to understand both the nature of matter and the interactions in the very part of phase diagram with relatively low temperature and high density. One of the most interesting questions which remain in that region concerns about the equation of state of nuclear matter. We can obtain direct information about the equation of state in the early stage of collisions via collective flow, which has been proved to be an effective way to study the nature of nuclear matter. Collective flow is commonly calculated in the form of Fourier expansion coefficients of particle azimuthal angle through event plane method.In this thesis we used IQMD model to simulate the typical non-central Au+Au collisions in sub-Ge V energy region and analyzed the collective anisotropic flow of the particles with the emphasis on studying the correlations between flow and the equation of state, beam energy, cross sections and symmetry energy term in mean field. We also analyzed the evolution of anisotropic flow together with the development of flow for particles in different windows of freeze-out time.The anisotropic flow from the simulated Au+Au collisions is very sensitive to the change of the equation of state and beam energies while less so when it comes to the term of cross section or symmetry energy. Still, there is an obvious difference between proton flow and neutron flow, which probably results from N-N cross section and the Coulomb potential in mean field. Anisotropic flow can be formed in the early stage of the collision, and be suppressed because of the interaction with spectators during the evolution. The flow of freeze-out nucleons can always reflect the information of collective motions of the very stage of collision, despite that the early freeze-out particles could not be used to deduce flow due to its tiny number. The work of this thesis is a prediction of the coming CSR External-target Experiment, which will be the only heavy ion collider working on sub-Ge V energy region in China.