Speaker
Description
The neutron-proton effective mass splitting (Δm*np) is investigated through analyses of heavy-ion collisions using the improved quantum molecular dynamics (ImQMD) model with both standard and extended Skyrme interactions. We find a strong correlation between the slope of the neutron-to-proton yield ratio with respect to the kinetic energy (i.e., Sn/p) and Δm*np, with correlation coefficients exceeding 0.80. For the ¹²⁴Sn + ¹²⁴Sn system, this correlation reaches 0.928. By comparing theoretical predictions with experimental data, we reveal a novel dependence of the neutron-proton effective mass splitting on momentum: at low kinetic energies, the data favor m*n > m*p, which is consistent with the nucleon-nucleus scattering analysis, while at high kinetic energies, they favor m*n < m*p, which is an extended understanding of effective mass splitting at high kinetic energy region. This finding provides the first direct evidence that the momentum-dependent symmetry potential likely decreases initially and then increases with momentum.
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