Probing neutron–proton effective mass splitting using nuclear stopping and isospin mix in heavy-ion collisions in GeV energy region

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The ramifications of the effective mass splitting on the nuclear stopping and isospin tracer during heavy-ion collisions within the gigaelectron volt energy region are studied using an isospin-dependent quantum molecular dynamics model. Three isotope probes, i.e., a proton, deuteron, and triton, are used to calculate the nuclear stopping. Compared to the $$m_\text {n}^{*} > m_\text {p}^{*}$$ case, the $$m_\text {n}^{*} < m_\text {p}^{*}$$ parameter results in a stronger stopping for protons but a weaker stopping for tritons. The calculations of the isospin tracer show that the $$m_\text {n}^{*} > m_\text {p}^{*}$$ parameter results in a higher isospin mix than the $$m_\text {n}^{*} < m_\text {p}^{*}$$ parameter. The rapidity and impact parameter dependences of the isospin tracer are also studied. A constraining of the effective mass splitting using the free nucleons with high rapidity and in a central rather than peripheral collision is suggested.