标题： 最大熵方法下格点QCD中激发核的谱分析 显示英文标题

标题： Spectral Analysis of Excited Nucleons in Lattice QCD with Maximum Entropy Method

摘要： 我们利用格点QCD模拟研究了激发态重子的质量谱。我们将注意力集中在正宇称激发态N'(1440)（Roper共振）和负宇称激发态N^*(1535)之间的能级排列问题上。通过结合具有周期性和反周期性边界条件的夸克传播子，在时间方向上实现了近乎完美的宇称投影。然后我们利用最大熵方法从格点数据中提取出谱函数。我们观察到对于广泛的夸克质量范围(M_pi=0.61-1.22 GeV)，N'和N^*态的质量非常接近，这与夸克模型的唯象预测相反。还研究了威尔逊双重子在重子谱函数中的作用。 显示英文摘要

摘要： We study the mass spectra of excited baryons with the use of the lattice QCD simulations. We focus our attention on the problem of the level ordering between the positive-parity excited state N'(1440) (the Roper resonance) and the negative-parity excited state N^*(1535). Nearly perfect parity projection is accomplished by combining the quark propagators with periodic and anti-periodic boundary conditions in the temporal direction. Then we extract the spectral functions from the lattice data by utilizing the maximum entropy method. We observe that the masses of the N' and N^* states are close for wide range of the quark masses (M_pi=0.61-1.22 GeV), which is in contrast to the phenomenological prediction of the quark models. The role of the Wilson doublers in the baryonic spectral functions is also studied.