Isospin Effects In Heavy Ion Collision At Intermediate Energy

Nuclear equation of state?EOS?is one of the most important subject in nuclear physics and astrophysics.It characterizes the relation among the temperature,density,size and energy of nuclear matters.The symmetry-energy term in the EOS controls not only the dynamics of nuclear reactions,the structure of the nucleus but also the structure of neutron stars and the evolution of supernovae,it is thus critical to understand the symmetry energy inside the EOS.However,there is still large uncertainty in the study of the relation between the symmetry energy and the density of nucleons.At the super-saturation region,different theories give different results.While,at the sub-saturation region,although theories are quite consistent with the experiments,there is still discrepancy among different theories.Efforts in both experiments and theories are needed to achieve deeper understanding in symmetry energy.And heavy ion collision is one of the most important methods in Laboratory.For this purpose,a 30 MeV/u⁴⁰Ar+¹⁹⁷Au experiment is performed in the RIBLL1terminal of HIRFL.In this thesis,we introduce in detail the setups of the experiment,the layout of the detectors and also the principles of each kind of detectors and the pretest results.In order to get the information of the isospin of the light charged particles emitted during the collision in different angles,which is related to the symmetry energy,every telescope in different angle is calibrated,and the identification of particles is performed using these data.From the results of the isospin information of light charged particles detected by the telescope,we find that the"neutronness"of the light charged particles will decrease as the polar angle is increase and vice versa,that is the isospin information of the emitted particle is closely related to the polar angle distribution.According to the multi-source model,we also find that the polar angle distribution of the multiplicity of certain kind of particle is related to the average emission time of the reaction.Thus,at the first time,we find that the isospin information in different polar angles can provide the information of the isospin transportation in a long time during the reaction.This helps to construct observables which is sensitive to the symmetry energy during a long time.Using the new-constructed observables Y_n,ex/Y_{p,C I}which indicates the"neutronness"of light charged particle emitted in different angle,we systematically investigate the symmetry energy over a large separation of the polar angle.Compared with the simulation results from ImQMD and GEMINI,we give the constraint of the?,which is the dependent parameter in the relation between symmetry energy and the density of nucleons,to be inside[0.4,0.5]which also corresponds to L=33-61MeV with the 95%confidence interval of when S=23.8MeV.