In the relativistic impulse approximation (RIA), we study symmetry potentials and in-medium nucleon-nucleon $\left(NN\right)$ cross sections with the Nambu–Jona-Lasinio (NJL) model that features chiral symmetry. The chiral symmetry that plays a fundamental role in the nonperturbative physics in the strong interaction is anticipated to add restrictive effects on the symmetry potentials and in-medium $NN$ cross sections. For comparison, we also perform the study with the usual relativistic mean-field (RMF) model. The numerical results with the NJL and RMF models are similar at saturation density and below, since a priori fit was made to saturation properties. With the increase of nuclear density, the chiral symmetry starts to be restored partially in the NJL model, resulting in the explicit fall of the scalar density. In a large energy span, the symmetry potential acquires a significant rise for the partial restoration of the chiral symmetry, compared to the one with the RMF model. It is found that the in-medium $NN$ cross sections in the RIA with the NJL and RMF models both increase with the density in the energy region interested in this study, whereas those with the NJL model increase sharply as long as a clear chiral symmetry restoration takes place. The different tendency of observables in density can be transmitted to the different energy dependence in the RIA. The NJL model is shown to have characteristic energy-dependent symmetry potentials and $NN$ cross sections beyond saturation point, apart from the RMF models.

中文翻译：

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相对论脉冲近似中 Nambu-Jona-Lasinio 模型中的对称势和介质中核子-核子截面

在相对论脉冲近似 (RIA) 中，我们研究对称势和介质中核子-核子 $\left(NN\right)$具有手征对称性的 Nambu-Jona-Lasinio (NJL) 模型的横截面。在强相互作用中的非微扰物理学中起着基本作用的手征对称性预计会增加对对称势和介质中的限制性影响。$NN$交叉区域。为了进行比较，我们还使用通常的相对论平均场 (RMF) 模型进行研究。NJL 和 RMF 模型的数值结果在饱和密度及以下相似，因为对饱和特性进行了先验拟合。随着核密度的增加，NJL模型中的手征对称性开始部分恢复，导致标量密度的显着下降。在大能量跨度中，与具有 RMF 模型的手征对称性的部分恢复相比，对称势获得显着上升。发现在中$NN$使用 NJL 和 RMF 模型的 RIA 中的横截面都随着本研究感兴趣的能量区域中的密度而增加，而使用 NJL 模型的横截面只要发生清晰的手征对称性恢复就会急剧增加。密度中可观察量的不同趋势可以传递到 RIA 中不同的能量依赖性。NJL 模型显示具有特征能量依赖的对称势和$NN$ 除了 RMF 模型之外，超过饱和点的横截面。