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Abstract: Within two different frameworks of isospin-dependent transport model, i.e., Boltzmann–Uehling–Uhlenbeck (IBUU04) and Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport models, sensitive probes of nuclear symmetry energy are simulated and compared. It is shown that neutron to proton ratio of free nucleons, ratio as well as isospin-sensitive transverse and elliptic flows given by the two transport models with their “best settings”, all have obvious differences. Discrepancy of numerical value of isospin-sensitive ratio of free nucleon from the two models mainly originates from different symmetry potentials used and discrepancies of numerical value of charged ratio and isospin-sensitive flows mainly originate from different isospin-dependent nucleon–nucleon cross sections. These demonstrations call for more detailed studies on the model inputs (i.e., the density- and momentum-dependent symmetry potential and the isospin-dependent nucleon–nucleon cross section in medium) of isospin-dependent transport model used. The studies of model dependence of isospin sensitive observables can help nuclear physicists to pin down the density dependence of nuclear symmetry energy through comparison between experiments and theoretical simulations scientifically. [Copyright &y& Elsevier]

Within the framework of the semiclassical Boltzmann-Uehling-Uhlenbeck transport model, we investigate the effects of symmetry energy on the sub-threshold pion using the isospin MDI interaction with the stiff and soft symmetry energies in the central collision of 48Ca+48Ca at the incident beam energies of 100, 150, 200, 250 and 300MeV/nucleon. We find that the ratio of π-/π+ of sub-threshold charged pion production is greatly sensitive to the symmetry energy, particularly around 100MeV/nucleon energies. Large sensitivity of sub-threshold charged pion production to nuclear symmetry energy may reduce uncertainties of probing nuclear symmetry energy via heavy-ion collision. [ABSTRACT FROM AUTHOR]

Abstract: Based on the isospin-dependent Boltzmann–Uehling–Uhlenbeck transport model coupled with the Lorentz force equation, we studied nucleus–nucleus collision in strong magnetic field. We find that neutrons and protons can be separated from a nucleus by strong magnetic field and neutron-rich high density nuclear matter and low density proton collectivity matter can be formed during nucleus–nucleus collision. The electric field produced by proton collectivity can accelerate proton and charged meson up to very high energies. Besides the studies of isospin physics such as symmetry energy, these results may help us to understand the acceleration mechanisms of high energy charged particles in the cosmic rays. [Copyright &y& Elsevier]

Based on the isospin-dependent transport model IBUU and on the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross-sections on $ \pi^{{-}}_{}$/ $ \pi^{{+}}_{}$ in the neutron-rich reaction Ca + Ca at a beam energy of 400MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect $ \Delta_{{1232}}^{}$ , $ \pi^{{-}}_{}$ and $ \pi^{{+}}_{}$ productions as well as the value of $ \pi^{{-}}_{}$/ $ \pi^{{+}}_{}$ . [ABSTRACT FROM AUTHOR]

Based on the modified isospin-dependent quantum molecular dynamics model, the number of emitted nucleons in a photonuclear reaction is studied with different symmetry potentials and different isospin-dependent nucleon-nucleon (N—N) collision cross sections. It is found that the number of emitted nucleons is sensitive to the isospin-dependent nucleon-nucleon cross section when the photon's energy is higher than 150MeV, while it is insensitive to symmetry potential. The number of emitted neutrons is more sensitive to N—N collision cross sections than that of protons. It is realized that the number of emitted neutrons can be used as a sensitive probe to extract the information of the isospin-dependent N—N cross section at high energy photonuclear reactions. [ABSTRACT FROM AUTHOR]

Abstract: Based on the isospin-and momentum-dependent hadronic transport model IBUU04, we have investigated the ratio in the following three reactions: 48Ca+48Ca, 124Sn + 124Sn and 197Au + 197Au with nearly the same isospin asymmetry but different masses, at the bombarding energies from 0.25 to 0.6 . It is shown that the sensitivity of probing the with increases with increasing the system size or decreasing the beam energy, showing a correlation to the degree of isospin fractionation. Therefore, with a given isospin asymmetry, heavier system at energies near the pion threshold is preferential to study the behavior of nuclear symmetry energy at supra-saturation densities. [Copyright &y& Elsevier]