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Feng Z.-Q.,CAS Lanzhou Institute of Modern Physics
Nuclear Physics A | Year: 2013

Strangeness (K0, +, Λ and σ -,0, +) production in heavy-ion collisions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model. The kaon (antikaon)-nucleon and hyperon-nucleon potentials in dense nuclear matter are implemented in the model, which are computed from the chiral perturbation approach and the relativistic mean-field model, respectively. It is found that the in-medium potentials change the structure of transverse flow, and also affect the rapidity distributions and the inclusive spectra for strangeness production. The local temperature of the fire ball extracted from the kaon spectra of inclusive invariant cross sections is influenced by the kaon-nucleon potential. The stiffness of nuclear symmetry energy and the kaon-nucleon potential by distinguishing isospin effect play a significant role on the ratio of K0/K +, in particular at the subthreshold energies. The ratio of σ -/σ + depends on the high-density symmetry energy, in which the σ-nucleon potential has a neglectable contribution on the isospin ratio. © 2013 Elsevier B.V. Source


Feng Z.-Q.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2013

Subthreshold kaon (K0 and K+) production in neutron-rich nuclear reactions to probe the kaon-nucleon interaction in nuclear medium and to extract the isospin-dependent part of the nuclear equation of state at high-baryon densities is investigated within an isospin- and momentum-dependent transport model. A repulsive kaon-nucleon potential is implemented in the model through fitting the flow data and inclusive spectra in heavy-ion collisions, which enhances the energetic kaon emission squeezed out in the reaction zone and leads to a variation of the high-momentum spectrum of the K0/K+ yields. It is found that the stiffness of nuclear symmetry energy plays a significant role on the isospin ratio with decreasing the incident energy and a hard symmetry energy has a larger value of the K0/K+ ratio in the domain of subthreshold energies. © 2013 American Physical Society. Source


Yong G.-C.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2011

Based on an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, effects of high-density behavior of nuclear symmetry energy in the proton-rich reaction 22Si+22Si at a beam energy of 400 MeV/nucleon are studied. It is found that the symmetry energy affects π+ production more than π-. More interestingly, compared to neutron-rich reactions, for π-/π+ and dense matter's N/Z ratios, effects of symmetry energy in the proton-rich reaction show contrary behaviors. The practical experiment by using the proton-rich reaction 22Si+40Ca to study nuclear symmetry energy is also provided. © 2011 American Physical Society. Source


Feng Z.-Q.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2011

The dynamics of pions and strange particles in heavy-ion collisions in the region of 1A GeV energies is investigated by the lanzhou quantum molecular dynamics model for probing the nuclear equation of state at suprasaturation densities. The total multiplicities and the ratios obtained in Au197 +197Au over C12+12C systems are calculated for selected Skyrme parameters SkP, SLy6, Ska, and SIII, which correspond to different modulus of incompressibility of symmetric nuclear matter and different cases of the stiffness of symmetry energy. A decreasing trend of the excitation functions of the ratios for strange particle production with increasing incident energy was observed. The available data of K+ production measured by KaoS collaboration are described well with the parameter SkP, which results in a soft equation of state. The conclusions cannot be modified by an in-medium kaon-nucleon potential. © 2011 American Physical Society. Source


Feng Z.-Q.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2011

A Skyrme-type momentum-dependent nucleon-nucleon force distinguishing isospin effect is parametrized and further implemented in the Lanzhou quantum molecular dynamics model, which leads to a splitting of nucleon effective mass in nuclear matter. Based on the isospin- and momentum-dependent transport model, we investigate the influence of momentum-dependent symmetry potential on several isospin-sensitive observables in heavy-ion collisions. It is found that symmetry potentials with and without the momentum dependence but corresponding to the same density dependence of the symmetry energy result in different distributions of the observables. The midrapidity neutron/proton ratios at high transverse momenta and the excitation functions of the total π-/π+ and K0/K+ yields are particularly sensitive to the momentum dependence of the symmetry potential. © 2011 American Physical Society. Source

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