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.
WANG JiaMA YugangZHANG GuoqiangFANG DeqingHAN LixinSHEN Wenqing
Isospin-dependent Quantum Molecular Dynamics model (IQMD) has been applied to investigate the Pygmy Dipole Resonance (PDR) and Giant Dipole Resonance (GDR) in Ni isotopes by Coulomb excitation. By Gaussian fitting to the photon emission spectra, the peak energies and strengths of PDR and GDR are extracted. Their sensitivities to impact parameter, incident energy and the symmetry energy are discussed. By the comparison of energy-weighted sum rule (EWSR) with the data and other calculations for 68 Ni, the parameters of density-dependence of symmetry energy in the IQMD are constrained. In addition, the N/Z dependence of PDR and GDR parameters of Ni isotopes are investigated, and the results that the EWSR increases linearly with the N/Z are obtained.
TAO ChengMA YugangZHANG GuoqiangCAO XiguangFANG DeqingWANG Hongwei
Dynamical dipole mode in heavy-ion collisions has been studied by using an isospin-dependent BoltzmannUehling-Uhlenbeck(IBUU) model. We investigate the dependence of centroid energy and strength of the γspectrum on beam energy, N/Z ratio and mass asymmetry. The calculated yield and angular distribution of theγ-ray produced by dynamical dipole emission are consistent with the experimental data. The results show that the detailed study of dynamical dipole radiation can provide information on the isospin evolution of chargeasymmetric heavy-ion collisions around the normal nuclear density.
By extending the minimum spanning tree(MST)clusterization algorithm for the binding energy cut,the isospin asymmetry dependence of directed flow for isospin sensitive isobar pairs(neutrons-protons,3H-3He) is studied from low towards high incident energies.The modified clusterization method(MSTB) has the advantage to identify the fragments at quite early time.It enhances(reduces) the production of free nucleons(fragments) over MST method.The directed flow of isobaric pair3H-3He is more sensitive towards isospin asymmetry caused by MSTB than isobaric pair n-p.This sensitivity becomes quite strong towards the high incident energy and neutron-rich reaction system.In conclusion,the inclusion of binding energy in clusterization method for the flow studies has been uniquely important for understanding the isospin physics,especially for high density behavior of symmetry energy.
