标题： 大-$N_c$ 分析介子无有效场论中的磁性和轴向两核子流 显示英文标题

标题： Large-$N_c$ analysis of magnetic and axial two-nucleon currents in pionless effective field theory

摘要： 我们分析了在结合大-$N_c$和无介子有效场论展开中的磁和轴向两核子接触项。 这些项在正确描述例如辐射中子俘获的低能截面和氘核磁矩中起着重要作用。 我们表明，大-$N_c$展开暗示了两个领先阶磁项之间存在一种层次关系，这与现象学拟合中发现的层次关系相匹配。 我们还对不同拉格朗日基中的自然性问题进行了评论。 显示英文摘要

摘要： We analyze magnetic and axial two-nucleon contact terms in a combined large-$N_c$ and pionless effective field theory expansion. These terms play important roles in correctly describing, e.g., the low-energy cross section of radiative neutron capture and the deuteron magnetic moment. We show that the large-$N_c$ expansion hints towards a hierarchy between the two leading-order magnetic terms that matches that found in phenomenological fits. We also comment on the issue of naturalness in different Lagrangian bases.