Zhuxia Li

The influence of cluster emission and the symmetry energy on neutron–proton spectral double ratios

Abstract The emissions of neutrons, protons and bound clusters from central 124 Snxa0+xa0 124 Sn and 112 Snxa0+xa0 112 Sn collisions are simulated using the Improved Quantum Molecular Dynamics model for two different density-dependent symmetry-energy functions. The calculated neutron–proton spectral double ratios for these two systems are sensitive to the density dependence of the symmetry energy, consistent with previous work. Cluster emission increases the double ratios in the low energy region relative to values calculated in a coalescence-invariant approach. To circumvent uncertainties in cluster production and secondary decays, it is important to have more accurate measurements of the neutron–proton ratios at higher energies in the center of mass system, where the influence of such effects is reduced.

Probing the symmetry energy with heavy ions

Abstract Constraints on the EoS for symmetric matter (equal neutron and proton numbers) at supra-saturation densities have been extracted from energetic collisions of heavy ions. Collisions of neutron-deficient and neutron-rich heavy ions now provide initial constraints on the EoS of neutron-rich matter at sub-saturation densities. Comparisons are made to other available constraints.

Constraints on nucleon effective mass splitting with heavy ion collisions

A new version of the improved quantum molecular dynamics model has been developed to include standard Skyrme interactions. Four commonly used Skyrme parameter sets, SLy4, SkI2, SkM* and Gs are adopted in the transport model code to calculate the isospin diffusion observables as well as single and double ratios of transverse emitted nucleons. While isospin diffusion observables are sensitive to the symmetry energy term, they are not very sensitive to the nucleon effective mass splitting parameters in the interactions. Our calculations show that the high energy neutrons and protons and their ratios from reactions at different incident energies provide a robust observable to study the momentum dependence of the symmetry potential which leads to the effective mass splitting. However the sensitivity of effective mass splitting effect on the double n/p yield ratios decreases with increasing beam energy, even though high energy protons and neutrons are produced more abundantly at high beam energy. Our calculations show that the optimum incident energy to study nucleon effective masses is between 100–200 MeV per nucleon.

Influence of in-medium NN cross sections, symmetry potential, and impact parameter on isospin observables

We explore the influence of in-medium nucleon-nucleon cross section, symmetry potential and impact parameter on isospin sensitive observables in intermediate-energy heavy-ion collisions with the ImQMD05 code, a modified version of Quantum Molecular Dynamics model. At incident velocities above the Fermi velocity, we find that the density dependence of symmetry potential plays a more important role on the double neutron to proton ratio

Effect of isospin-dependent cluster recognition on the observables in heavy ion collisions

DR(n/p)

Covariance analysis of symmetry energy observables from heavy ion collision

and the isospin transport ratio

Probing the symmetry energy with isospin ratio from nucleons to fragments

R_i

Constraints on the density dependence of the symmetry energy

than the in-medium nucleon-nucleon cross sections, provided that the latter are constrained to a fixed total NN collision rate. We also explore both

Probing the density dependence of symmetry energy at subsaturation density with HICs

DR(n/p)

Constraints on the Density Dependence of the Symmetry Energy

and