Research Of The Symmetry Energy Of Nuclear Matter In Heavy-ion Collisions

In this thesis, two methods are used to study the nuclear symmetry energy of sub-saturation matterand finite nucleus density, which are both produced in heavy ion collision. There are two main parts in thisthesis:(1)The n/p or double n/p ratio probes are used to test their sensitivity to the nuclear symmetry energy(NSE) parameters. The isospin-dependent quantum molecular dynamics (IQMD) model is used to simulatethe reactions by using different NSE parameters. The40,48Ca+58,64Ni at50and600MeV/n reactions arecalculated, and the kinetic energy spectra of neutron-to-proton single and double ratios are analyzed fordetail. A Xifactor is defined to universalize the sensitivity of the symmetry energy, and get the best probefor the sensitivity of isospin ratios towards the density dependence of symmetry energy. It isrecommended to use a neutron-rich projectile (target) in combination with a neutron-weak target (projectile)to observe the importance of the projectile (target) fragmentation regions in connection with the symmetryenergy effects by using the probe of double ratio from the projectile fragmentation region.(2) The isobars yield ration (IYR) method is developed to investigate the nuclear symmetry energycoefficient of finite nuclei. In the framework of the modified Fisher model, correlations between thesymmetry-energy coefficient in mass formula to temperature and the isobaric yield are established in1GeV/n124,136Xe+Pb reactions. Three methods are used to extract. It is found that the referenceisobars adopted have great influence on the extracted of fragments, and the Coulomb-energy termhas little effect on of fragments.