标题： 核子2s激发的物理解释 显示英文标题

标题： Physical interpretation of the 2s excitation of the nucleon

摘要： 格点QCD计算了核子的$2s$径向激发态，将该状态的能量置于约1.9 GeV处，这提出了它可能通过与介子-重子态的混合而与$N1/2^+(1880)$和$N1/2^+(1710)$共振态相关联的可能性。 在π光致产生中发现了$N1/2^+(1880)$共振态，但在$\pi N$散射中未发现，以及$N1/2^+(1710)$共振态的窄宽度表明，与这些共振态相关的态对允许π介子如何“穿衣”它的方法不敏感。 为了探索这种可能性，我们研究了在2+1味QCD中以及在通过淬火显著修改与介子-重子态耦合的模拟中核子径向激发态的谱。 我们发现，对于接近物理点的夸克质量，$2s$径向激发态的能量对该修改不敏感。 这种不变性进一步证明了核子的$2s$径向激发与$N1/2^+(1880)$和$N1/2^+(1710)$共振有关。 显示英文摘要

摘要： Lattice QCD calculations of the $2s$ radial excitation of the nucleon place the state at an energy of approximately 1.9 GeV, raising the possibility that it is associated with the $N1/2^+(1880)$ and $N1/2^+(1710)$ resonances through mixing with two-particle meson-baryon states. The discovery of the $N1/2^+(1880)$ resonance in pion photoproduction but not in $\pi N$ scattering and the small width of the $N1/2^+(1710)$ resonance suggest that a state associated with these resonances would be insensitive to the manner in which pions are permitted to dress it. To explore this possibility, we examine the spectrum of nucleon radial excitations in both 2+1 flavour QCD and in simulations where the coupling to meson-baryon states is significantly modified through quenching. We find the energy of the $2s$ radial excitation to be insensitive to this modification for quark masses close to the physical point. This invariance provides further evidence that the $2s$ radial excitation of the nucleon is associated with the $N1/2^+(1880)$ and $N1/2^+(1710)$ resonances.