arXiv subjects

Li Ou

Publications and source records attributed to Li Ou.

23 records · Page 2Linked to original sources

arXiv2014

Mechanism of production of light complex particles in nucleon-induced reactions

The Improved Quantum Molecular Dynamics (ImQMD) model incorporated with the statistical decay model is successful in describing emission of nucleons in the intermediate energy spallation reactions, but not good enough in describing productions of light complex particles, i.e. $d$, $t$, $^3$He and $^4$He. To improve the description on emission of light complex particles, a phenomenological mechanism called surface coalescence and emission is introduced into ImQMD model: nucleon ready to escape from the compound nuclei can coalesce with the other nucleon(s) to form light complex particle and be emitted. With updated ImQMD model, the description on the experimental data of light complex particles produced in nucleon-induced reactions are great improved.

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arXiv2014

Sensitive dependence of isotope and isobar distribution of limiting temperatures on symmetry energy

The mass, isotope, and isobar distributions of limiting temperatures for finite nuclei are investigated by using a thermodynamics approach together with the Skyrme energy density functional. The relationship between the width of the isotope (isobar) distribution of limiting temperatures and the stiffness of the density dependence of the symmetry energy clearly is observed. The nuclear symmetry energy with smaller slope parameter $L_{\rm{sym}}$ causes a wider the isotope (isobar) distribution of limiting temperatures. The widths of the isotope (isobar) distributions of limiting temperatures could be useful observables for exploring the information of the density dependence of the nuclear symmetry energy at finite temperatures.

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arXiv2013

Nuclear symmetry energy from the Fermi-energy difference in nuclei

The neutron-proton Fermi-energy difference and the correlation to nucleon separation energies for some magic nuclei are investigated with the Skyrme energy density functionals and nuclear masses, with which the nuclear symmetry energy at sub-saturation densities is constrained from 54 Skyrme parameter sets. The extracted nuclear symmetry energy at sub-saturation density of 0.11 fm$^{-3}$ is 26.2 $\pm$ 1.0 MeV with 1.5 $σ$ uncertainty. By further combining the neutron-skin thickness of 208Pb, ten Skyrme forces with slope parameter of 28<L<65 are selected for the description of the symmetry energy around saturation densities.

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arXiv2011

Magnetic effects in heavy-ion collisions at intermediate energies

The time-evolution and space-distribution of internal electromagnetic fields in heavy-ion reactions at beam energies between 200 and 2000 MeV/nucleon are studied within an Isospin-dependent Boltzmann-Uhling-Uhlenbeck transport model IBUU11. While the magnetic field can reach about $7\times 10^{16}$ G which is significantly higher than the estimated surface magnetic field ($\sim 10^{15}$ G) of magnetars, it has almost no effect on nucleon observables as the Lorentz force is normally much weaker than the nuclear force. Very interestingly, however, the magnetic field generated by the projectile-like (target-like) spectator has a strong focusing/diverging effect on positive/negative pions at forward (backward) rapidities. Consequently, the differential $π^-/π^+$ ratio as a function of rapidity is significantly altered by the magnetic field while the total multiplicities of both positive and negative pions remain about the same. At beam energies above about 1 GeV/nucleon, while the integrated ratio of total $π^-$ to $π^+$ multiplicities is not, the differential $π^-/π^+$ ratio is sensitive to the density dependence of nuclear symmetry energy $E_{\rm{sym}}(ρ)$. Our findings suggest that magnetic effects should be carefully considered in future studies of using the differential $π^-/π^+$ ratio as a probe of the $E_{\rm{sym}}(ρ)$ at supra-saturation densities.

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arXiv2010

Effect of splitting of the neutron and proton effective mass on nuclear symmetry energy at finite temperature

We present the temperature and density dependence of symmetry energy for nuclear matter at finite temperature based on the approach of the thermodynamics with Skyrme energy density functional. We first classify the Skyrme interactions into 7 groups according to the range of neutron and proton effective mass in neutron matter limit(99.99 per cent neutron in the matter). We find that there is obvious correlation between the temperature dependence of the symmetry energy and the splitting of the neutron and proton effective mass. For some Skyrme interactions with $m^{*}_{n}>m^{*}_{p}$ and strong splitting of the neutron and proton effective mass in asymmetric nuclear matter, a transition of the temperature dependence of symmetry energy from decreasing with temperature at low densities to increasing with temperature at high densities appears. For other Skyrme interactions, we do not observe such phenomenon. Our study show that the symmetry energy in hot asymmetric matter not only depends on symmetry potential part but also on the splitting of the neutron and proton effective mass to a certain extent.

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