Nuclear in-medium effects and collective flows in heavy-ion collisions at intermediate energies

A recent updated version of Lanzhou quantum molecular dynamics, in which the momentum dependence of the symmetry potential and the effective mass splitting of protons and neutrons in the nuclear medium are included in the model, is reviewed,. The in-medium nucleon-nucleon (NN) elastic cross sections are evaluated with the scaling approach according to the effective mass and their influence on collective flows in heavy-ion collisions are discussed. The inelastic cross sections, in particular for the process of the channel N Delta -> NN, are parametrized in accordance with the available experimental data. It is found that the in-medium cross sections play a significant role in isospin emission and result in a flatter distribution for transverse flows and elliptic flows of free nucleons compared with the in-vacuum ones. The rapidity distribution of the difference between neutron and proton transverse flows is sensitive to the stiffness of the nuclear symmetry energy as a promising observable, which cannot be influenced by the in-medium effect and collision centrality. Furthermore, the elliptic flow of free energetic nucleons in the case of the mass splitting of m*(n) > m*(p) is also related to the symmetry energy. However, the pion flows weakly depend on the symmetry energy and the mass splitting.