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Abstract The nuclear symmetry energy, especially at suprasaturation densities, plays crucial roles in many astrophysical studies. However, nowadays the high-density behavior of the symmetry energy is still very controversial in nuclear community. To constrain the high-density behavior of the symmetry energy, neutron-rich nuclei collisions at medium energies are considered to be one of the most effective methods. While probing the high-density symmetry energy by using heavy-ion collisions, blind spots may exist. In the framework of the Isospin-dependent Boltzmann–Uehling–Uhlenbeck (IBUU) transport model, the blind spots of probing the high-density symmetry energy by the n/p ratio in the central Au + Au reaction at 300 MeV / nucleon are demonstrated. It is found that the nucleon observable neutron to proton ratio n/p in heavy-ion collisions cannot effectively probe the high-density symmetry energy when the high-density symmetry energy is less density-dependent. [ABSTRACT FROM AUTHOR]

It is theoretically and experimentally argued that there may exist bubble or toroid-shaped configurations in some nucleus systems. Based on the isospin-dependent transport model of nucleus-nucleus collisions, here we propose a method to probe the bubble configuration in the nucleus. That is, one could use the value of the $ \pi^{-} / \pi^{+}$ ratio especially its kinetic energy distribution in head-on collision at intermediate energies to probe whether there is bubble configuration or not in projectile and target nuclei. Due to different maximum compressions and the effect of symmetry energy, the value of the $\pi^{-} / \pi^{+}$ ratio in the collision of bubble nuclei is evidently larger than that in the collision of normal nuclei. [ABSTRACT FROM AUTHOR]

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: Hard photon production from neutron–proton bremsstrahlung in intermediate energy heavy-ion reactions is examined as a probe of the in-medium pn scattering cross section within a transport model. Uncertainty of photon production probability is cancelled out by using the ratio of hard photon spectra from two reactions. The in medium pn scattering cross section is constrained by using the ratio of hard photon production cross sections of proton-induced reactions and . A reduction factor of about 0.5–0.7 around saturation density is obtained by comparing with the existing experimental data. [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]

We review recent progress in the determination of the subsaturation density behavior of the nuclear symmetry energy from heavy-ion collisions as well as the theoretical progress in probing the high density behavior of the symmetry energy in heavy-ion reactions induced by high energy radioactive beams. We further discuss the implications of these results for the nuclear effective interactions and the neutron skin thickness of heavy nuclei. [ABSTRACT FROM AUTHOR]

Abstract: The nuclear symmetry energy is the most uncertain part of the Equation of State (EOS) of dense neutron-rich nuclear matter. In this talk, we discuss the underlying physics responsible for the uncertain especially at supra-saturation densities, the circumstantial evidence for a super-soft from analyzing ratio in relativistic heavy-ion collisions and its impacts on astrophysics and cosmology. [Copyright &y& Elsevier]