Studies Of Particle Momentum Correlation Function And Nucleon-number Scaling For Collective Flow And Nuclear Modification Factor In Squeeze-out Region In Intermediate Energy Heavy Ion Collision

One major aim of heavy ion collisions is to reveal the properties of nuclear matter under extreme hot,dense,isospin conditions.In intermediate and high energy heavy ion collision,the frontier of nuclear physics research includes nuclear reaction mechanism,the nature of dense nuclear matter and nuclear equation of state.Among them,the intermediate energy heavy ion collision process mainly includes the reaction dynamics and statistical decay process.The former includes a collective motion,and the later primarily focuses on process of thermal equilibrium at local equilibrium.Concerning the reaction dynamics,anisotropic flows become a hot topic of high energy heavy ion collisions.Momentum correlation function between the two particles contains the early dynamic information of collision,in addition,the correlation functions between the light fragments carry more information about the heavy ion collisions dynamics.In this paper,the isospin-dependent quantum molecular dynamics model?IQMD?is applied to study the dynamic process of intermediate energy heavy ion collision.The main work has three parts:Firstly,we explore the number of nucleon?NN?scaling of the directed flow₁ and elliptic flow?₂?as well as the nuclear modification factor?ccp?in intermediate energy heavy ion collision,especially for the squeeze-out region.The above abservables are tested for light nuclei which are produced in 0.4A GeV Au+Au collisions at different impact parameters with different in-medium nucleon-nucleon cross sections in a framework of an isospin-dependent quantum molecular dynamics model.In that energy domain,the emission of light nuclei can be well described by the squeeze-out phenonomenon.The results show a nice NN scaling behavior for flow parameters₁,₂ and ccp.These results demonstrate that the nucleon coalescence mechanism is responsible for nucleon-number scaling of above physical observables in squeeze-out region in heavy-ion collisions at intermediate energy.Secondly,the proton-proton momentum correlation function from different rapidity regions is systematically investigated for the Au+Au collisions at different impact parameters and different energies from 0.4A GeV to 1.5A GeV in the framework of the isospin-dependent quantum molecular dynamics model complemented by the Lednicky-Lyuboshitz analytical method.In particular,the in-medium nucleon-nucleon cross-section dependence of the correlation function is brought into focus,while the impact parameter and energy dependence of the momentum correlation function are also explored.The sizes of the emission source are extracted by fitting the momentum correlation functions using the Gaussian source method.We find that the in-medium nucleon-nucleon cross section obviously influences the proton-proton momentum correlation function,which is from the whole-rapidity or projectile or target rapidity region at smaller impact parameters,but there is no effect on the mid-rapidity proton-proton momentum correlation function,which indicates that the emission mechanism differs between projectile or target rapidity and mid-rapidity protons.Finally,momentum correlation function at small relative momenta is calculated for light charged particles?p;d;t?emitted from Au+Au collisions at different impact parameters and beam energies within the framework of the isospin-dependent quantum molecular dynamics model complemented by the Lednicky-Lyuboshitz analytical method.We first make sure our model is able to reproduce the FOPI data of proton-proton momentum correlation in a wide energy range from 0.4A GeV to 1.5A GeV.Then we explore more physics insights through the emission times and momentum correlations among different light charged particles.The specific emphasize is the effects of total pair momentum among different light particles,impact parameters and in-medium nucleon-nucleon cross section.Both two-deuteron and two-triton correlation functions are anti-correlation due to the final state interaction,and they are sensitive to the higher total momentum of the particle pairs,but not to the lower ones.In addition,impact parameter and in-medium nucleon-nucleon cross section dependences of the emission source radii are extracted by fitting the momentum correlation functions.The results indicate that total momentum gated dependence of the momentum correlation functions is stronger for the smaller in-medium nucleon-nucleon cross section factor???or impact parameter?b?.Non-identical particle correlations?p-d;p-t;and d-t?are also investigated by the velocity-gated correlation functions which can give information of the particles'emission sequence,and the result indicates that heavier ones?deuteron/triton?are,on the average,emitted earlier than protons,in the small relative momentum region.