分类: 物理学 >> 核物理学 提交时间: 2024-02-24
摘要: The yield ratios of neutron-proton (R(n/p)) and 3H-3He (R(3H/3He)) with reduced rapidity from 0 to 0.5 were simulated for 50 MeV/u even-even 36-56Ca + 40Ca, even-even 48-78Ni + 58Ni and 100-139Sn (every third isotopes) + 112Sn at full reduced impact parameters using the isospin-dependent quantum molecular dynamics (IQMD) model. The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model, which was used for the phase space initialization of the projectile and target in IQMD. We defined the unified neutron skin thickness as ΔRnp=2>n1/2-2>p1/2, which was negative for neutron-deficient nuclei. The unified ΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal, except for extreme neutron-rich isotopes, which is a type of scaling behavior. The yield ratios of the three isotopic chains-induced reactions, which dependent on the reduced impact parameter and the unified neutron skin thickness, were studied. The results show that both R(n/p) and R(3H/3He) decreased with a reduced impact parameter for extreme neutron-deficient isotopes; however, they increased with reduced impact parameters for extreme neutron-rich isotopes, and increased with the ΔRnpof the projectiles for all reduced impact parameters. In addition, a scaling phenomena was observed between ΔRnp and the yield ratios in peripheral collisions from different isotopic chain projectiles (except for extreme neutron-rich isotopes). Thus, R(n/p) and R(3H/3He) from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.
分类: 物理学 >> 核物理学 提交时间: 2023-10-24
摘要: The Zero Degree Calorimeter (ZDC) plays a crucial role in determining centrality at the Cooling-Storage-Ring External-target Experiment (CEE) in the Heavy Ion Research Facility in Lanzhou (HIRFL). A Boosted Decision Trees (BDT) multi-classification algorithm is employed to classify the centrality of the collision events based on the raw features from ZDC such as the number of fired channels and deposited energy. The data from simulated $ rm ^{238}U$ + $ rm ^{238}U$ collisions at 500 $ rm MeV/u$, generated by the IQMD event generator and subsequently modeled through the GEANT4 package, is employed to train and test the BDT model. The results showed the high accuracy of the multi-classification model adopted in ZDC for centrality determination, which is robust against variations in different factors of detector geometry and response. The study demonstrates a good performance of the CEE-ZDC for determining the centrality in nucleus-nucleus collisions.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: How the initial fluctuation affects on the elliptic flow is investigated by investigating the rapidity, transverse 4-velocity, centrality dependencies of elliptic flow for Au+Au at 1 GeV/A with the help of an Isospin Quantum Molecular Dynamics (IQMD). In addition, we compare the flow calculated with respect to participant plane created by the initial geometry in coordinate space with the flow reconstructed by the experimental event-plane method, and compare the flow with the experimental data of the FOPI collaboration. It shows that there exists some discrepancy between the flows reconstructed by the above two methods.