Guo Wen-Jun

Total nuclear reaction cross section induced by halo nuclei and stable nuclei

We develop a method for calculation of the total reaction cross sections induced by the halo nuclei and stable. nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energies. It is extended for nuclear reactions at low energies and intermediate energies by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with 30 experimental data within 10 percent accuracy. The comparison between the numerical results and 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root-mean-square radii of these nuclei can be extracted from the above comparison based on the improved Glauber model, which indicates clearly the halo structures of these nuclei. Especially, it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very, weak binding and the very extended density distribution.We develop the method for the calculation of the total reaction cross sections induced by the halo nuclei and stable nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energy. It is extended for nuclear reactions at low energy and intermediate energy by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with the 30 experimental data within 10 percent accuracy.The comparison between the numerical results and the 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies the quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root mean square radii of these nuclei can be extracted from above comparison based on the improved Glauber model, which indicate clearly the halo structures of these nuclei. Especially, it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very weak binding and the very extended density distribution.

Entrance channel dependence of the isospin effects of the nuclear stopping in intermediate energy heavy-ion collisions

The entrance channel dependence of the isospin effects of nuclear stopping in intermediate energy heavy-ion collisions has been studied by using an isospin-dependent quantum molecular dynamics with three different kinds of symmetry potentials. It is shown that nuclear stopping is sensitive to the beam energy, the impact parameter and the mass of the colliding system, especially very sensitive to the isospin dependence of the in-medium nucleon-nucleon cross section, but insensitive to the symmetry potential and the neutron-to-proton ratio of the colliding system. From this investigation, it is proposed that nuclear stopping can be used as a new probe to extract the information on the isospin dependence of the in-medium nucleon-nucleon cross section in intermediate energy heavy-ion collisions.

Isospin Effects of the Mean Field and Two-Body Collision on the Fragmentation Process

Isospin effects of the mean field and two-body collision on the fragmentation as well as their dependences on the momentum-dependent interaction at intermediate energy heavy ion collisions are studied by using an isospin-dependent quantum molecular dynamics model. We find the prominent isospin effects of the multiplicity of the intermediate mass fragments Nimf, where Nimf depends sensitively on the isospin effect of the in-medium nucleon-nucleon cross section and weakly on the variation of symmetry potential in the intermediate energy region. The momentum dependence interaction enhances the sensitivity of Nimf on the isospin effect of two-body collision.

Isospin Momentum-Dependent Interaction and Its Role on the Isospin Fractionation Ratio in Intermediate Energy Heavy Ion Collisions

We investigate the role of isospin momentum-dependent interaction on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions, by inserting an isospin degree of freedom into the momentum-dependent interaction to obtain an isospin momentum-dependent interaction given in a form practically usable in the isospin-dependent quantum molecular dynamics model. It is found that the isospin momentum-dependent interaction brings an important isospin effect into the isospin fractionation ratio. In particular, the isospin momentum-dependent interaction reduces obviously the reduction of isospin fractionation ratio. Thus the isospin dependence of momentum-dependent interaction is thus important for studying accurately the equation of state of isospin asymmetry nuclear matter.

Isospin Effect of Coulomb Interaction on Momentum Dissipation in Intermediate Energy Heavy Ion Collisions

We investigate the isospin effect of Coulomb interaction on the momentum dissipation or nuclear stopping in the intermediate energy heavy ion collisions by using the isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces obviously the reductions of the momentum dissipation. We also find that the variation amplitude of momentum dissipation induced by the Coulomb interaction depends sensitively on the form and strength of symmetry potential. However, the isospin effect of Coulomb interaction on the momentum dissipation is less than that induced by the in-medium nucleon–nucleon cross section. In this case, Coulomb interaction does not change obviously the isospin effect of momentum dissipation induced by the in-medium two-body collision. In particular, the Coulomb interaction is preferable for standing up the isospin effect of in-medium nucleon–nucleon cross section on the momentum dissipation and reducing the isospin effect of symmetry potential on it, which is important for obtaining the feature about the sensitive dependence of momentum dissipation on the in-medium nucleon–nucleon cross section and weakly on the symmetry potential.

Effect of Coulomb Interaction on the Isospin Fractionation Process

We studied the effect of Coulomb interaction on the isospin fractionation in the intermediate energy heavy ion collisions by using the isospin-dependent quantum molecular dynamics model. The calculated results show that Coulomb interaction induces the reduction of the isospin fractionation process with the evolutions of neutron–proton ratio and mass of system. Because Coulomb interaction is repulsive for the proton, more binding protons become free, which produces the neutron-poor gas phase and neutron-rich liquid phase, compared to the neutron–proton ratio of the system. The isospin fractionation degree is weakened by the Coulomb term. In contrast, the symmetry potential is repulsive for neutrons and attractive for protons in the neutron-rich system, and then the binding neutrons more than the protons become free, which produces a neutron-rich gas phase and neutron-poor liquid phase, so that the isospin fractionation degree is increased. The competition between the effects from the Coulomb interaction and the symmetry potential induces the reduction of the isospin fractionation degree for all the system masses. The properties for the sensitive dependence of isospin fractionation degree on the symmetry potential and weak dependence on the nucleon–nucleon cross section are preserved for all the neutron-rich systems.

Probing of the Isospin-Dependent Mean Field and Nucleon-Nucleon Cross Section in a Medium by Nucleon Emissions

Institute for the theory of modern physics, Tianshui Normal University, Gansu, Tianshui 741000, P. R. China Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator Lanzhou 730000, P.R. China Institute of Modern Physics, Chinese Academy of Sciences, P.O.Box 31 Lanzhou 730000, P.R. China CCAST(Word Lab.),P.O.Box 8730,Beijing 100080 Lanzhou 730000, P.R. China We study the isospin effects of the mean field and two-body collision on the nucleon emissions at the intermediate energy heavy ion collisions by using an isospin dependent transport theory. The calculated results show that the nucleon emission number Nn depends sensitively the isospin effect of nucleon nucleon cross section and weakly on the isospin dependent mean field for neutron-poor system in higher beam energy region . In particular ,the correlation between the medium correction of two-body collision and the momentum dependent interaction enhances the dependence of nucleon emission number Nn on the isospin effect of nucleon nucleon cross section. On the contrary, the ratio of the neutron proton ratio of the gas phase to the neutron proton ratio of the liquid phase ,i.e., the degree of isospin fractionation < (N/Z)gas >b / < (N/Z)liq >b depends sensitively on the isospin dependent mean field and weakly on the isospin effect of two-body collision for neutron-rich system in the lower beam energy region. In this case, Nn and < (N/Z)gas >b / < (N/Z)liq >b are the probes for extracting the information about the isospin dependent nucleon nucleon cross section in the medium and the isospin dependent mean field,respectively. PACS number(s): 25·70·PqWe study the isospin effects of the mean field and two-body collision on the nucleon emissions at the intermediate energy heavy-ion collisions by using an isospin-dependent transport theory. The calculated results show that the nucleon emission number Nn depends sensitively on the isospin effect of nucleon-nucleon cross section and weakly on the isospin-dependent mean field for neutron-poor system in higher beam energy region. In particular, the correlation between the medium correction of two-body collision and the momentum-dependent interaction enhances the dependence of nucleon emission number Nn on the isospin effect of nucleon-nucleon cross section. On the contrary, the ratio of the neutron-proton ratio of the gas phase to the neutron-proton ratio of the liquid phase, i.e., the degree of isospin fractionation (N/Z)gasb/(N/Z)liqb depends sensitively on the isospin-dependent mean field and weakly on the isospin effect of two-body collision for neutron-rich system in the lower beam energy region. In this case, Nn and (N/Z)gasb/(N/Z)liqb are the probes for extracting the information about the isospin-dependent nucleon-nucleon cross section in the medium and the isospin-dependent mean field, respectively.

Medium Influence of the Nucleon-Nucleon Cross Section on the Fragmentation

Based on an isospin-dependent quantum molecular dynamics model we studied the influence of a medium correction of an isospin-dependent nucleon-nucleon cross section on the fragmentation at the intermediate energy heavy-ion collisions. We found that the medium correction from an isospin-dependent nucleon-nucleon cross section increases the dependence of the fragmentation on the isospin effect of in-medium nucleon-nucleon cross section, at the same time, the momentum-dependent interaction also produces an important role for enhancing the influence of the medium correction on the isospin effect of two-body collisions in the fragmentation process.Institute for the theory of modern physics, Tianshui Normal University, Gansu, Tianshui 741000, P. R. China Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator Lanzhou 730000, P.R. China Institute of Modern Physics, Chinese Academy of Sciences, P.O.Box 31 Lanzhou 730000, P.R. China CCAST(Word Lab.),P.O.Box 8730,Beijing 100080 Lanzhou 730000, P.R. China Based on an isospin dependent quantum molecular dynamics model we studied the influence of a medium correction of an isospin dependent nucleon nucleon cross section on the fragmentation at the intermediate energy heavy ion collisions. We found that the medium correction from an isospin dependent nucleon nucleon cross section increases the dependence of the fragmentation on the isospin effect of in-medium nucleon nucleon cross section, at the same time, the momentum dependent interaction (MDI) produces also an important role for enhancing the influence of the medium correction on the isospin effect of two-body collisions in the fragmentation process. PACS number(s): 25·70·pq Correspond auther: E-mail address: Liujy@ns.lzb.ac.cn Phone number:86-0931-4969318(O),8272215(H). Fax number:86-0931-4969201