Dynamical origin of universal two-pole structures and their light quark mass evolution

¹ School of Physics, Beihang University, Beijing 102206, China
² Peng Huanwu Collaborative Center for Research and Education, Beihang University, Beijing 100191, China
³ Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 102206, China
⁴ Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences, Huizhou 516000, China
⁵ CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
⁶ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
⁷ School of Physics, Peking University, Beijing 100871, China

^* e-mail: lisheng.geng@buaa.edu.cn

Published online: 25 September 2024

Abstract

Two-pole structures refer to the fact that two dynamically generated states are located close to each other between two coupled channels and have a mass difference smaller than the sum of their widths. Thus, the two poles overlap in the invariant mass distribution of their decay products, creating the impression that only one state exists. This phenomenon was first noticed for the Λ(1405) and the K₁(1270), and then for several other states. This report explicitly shows how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between a heavy matter particle and a pseudo-Nambu-Goldstone boson. Furthermore, we predict similar two-pole structures in other systems dictated by chiral symmetry, such as the isospin 1/2 K¯∑_c − πΞ^′_c coupled channel, awaiting experimental discoveries.