Spin-orbit coupling in intermediate-energy heavy-ion collisions

Background: Nuclear spin-orbit interaction is important in understanding magic number and shell structure of finite nuclei. Although it has been extensively studied in nuclear structure, its effect in nuclear reactions was long overlooked. Purpose: To be consistent, same nuclear force should be used in both studies of nuclear structure and nuclear reactions. Heavy-ion collisions provide more freedom to study the detailed properties of in-medium nuclear spin-orbit interaction. Methods: In this proceeding, we summarize our recent studies on introducing nucleon spin degree of freedom and spin-related mean-field potentials from nuclear spin-orbit interaction into IBUU (Isospin-dependent Boltzmann-Uehling-Uhlenbeck) transport model. Results: The spin differential transverse flow is sensitive to the strength of the spin-orbit coupling and serves as a useful probe for in-medium spin-orbit interaction. The difference of the spin differential transverse flow for neutrons and protons can be used to study the isospin dependence of the spin-orbit coupling, while spin differential flow of nucleons with high transverse momentum at different beam energies can be used to exact information of the density dependence of the nuclear spin-orbit interaction. Conclusion: With more spin-related probes proposed in the near future, intermediate-energy heavy-ion collisions may become a useful method in studying in-medium nuclear spin-orbit interaction. (authors)