https://doi.org/10.1140/epjc/s10052-021-09329-9
Letter
Two-pole structures in a relativistic Friedrichs–Lee-QPC scheme
1
School of Physics, Southeast University, 211189, Nanjing, People’s Republic of China
2
NSFC-SFTP Peng Huanwu Center for Fundamental Theory and Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, 230026, Hefei, Anhui, People’s Republic of China
Received:
5
November
2020
Accepted:
13
June
2021
Published online:
26
June
2021
A general appearance of two-pole structures is exhibited in a relativistic Friedrichs–Lee model combined with a relativistic quark pair creation model in a consistent manner. This kind of two-pole structure could be found when a 
state couples to the open-flavor continuum state in the S partial wave. We found that many enigmatic states, such as 
, 
, 
, 
, 
, 
, and X(3872), together with another higher state for each, all result from this kind of two-pole structures. Furthermore, an interesting observation is that this kind of two-pole structure will contribute roughly a total of 
phase shift for the scattering process in a single channel approximation. This relativistic scheme may provide more insights into the understanding of the properties of non- state. It is also suggested that such two-pole structure could be a common phenomenon which deserves studying both from theoretical and experimental perspectives.
© The Author(s) 2021
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