对基态重子-介子相互作用的研究不仅能够检验我们对于低能强相互作用的理解，还有助于揭示重子本身以及奇特强子态的性质，并与重子-重子相互作用密切相关。手征微扰理论及其幺正化方法已被成功应用于描述piN，KN弹性散射数据，揭示Λ(1405)的双极点结构。然而，基于次领头阶势场，基于不同模型拟合不同KbarN散射数据得到的Λ(1405)双极点位置却存在较大的差异。申请人计划开展以下研究：将KbarN非微扰散射振幅在协变框架下计算至次次领头阶，首次考虑来自piN，KN弹性散射相移的限制进行全局拟合，确定拉氏量中至次次领头阶全部相关的低能常数，给出Λ(1405)双极点的准确位置，预言其它反应道散射振幅，研究其中非微扰效应，并拓展研究重味重子激发态以及五夸克态。进一步结合机器学习技术，评估选取不同模型拟合不同数据带来的不确定度，高精度地描述重子-介子相互作用。

The studies on meson-baryon interactions can not only examine our understanding on the low-energy strong interactions, but also be helpful for revealing the static properties of baryons and exotic baryons. It is also tightly related to the baryon-baryon interactions. Chiral perturbation theory and its unitary version have been applied to describe the piN and KN elastic scattering phase shifts and interpret the double-pole structure of Λ(1405). However, based on the next-to-leading order potential, the positions of the two Λ(1405) resonances obtained from different models and different KbarN scattering data differ a lot. The applicant plans to calculate the KbarN scattering amplitudes up to next-to-next-to-leading order and perform a global fit taking into account the stringent constraints from the piN and KN elastic phase shifts. With all the LECs up to NNLO being fixed, we can unambiguously determine the positions of Λ(1405). Studies on the scattering amplitudes as well as the non-perturbation phenomenon in other channels will be performed. Similar methods will be developed to study the heavy flavor excited baryons and penta-quark states. Furthermore, uncertainties due to the choice of different sets of data and models will be investigated with the techniques from machine learning.