Photo- and electro-production of narrow exotic states: From light quarks to charm and up to bottom

Abstract

Accessing a full image of the inner content of hadrons represents a central endeavour of modern particle physics, with the main scientific motivation to investigate the strong interaction binding the visible matter. On the one hand, the structure of known exotic candidates is a fundamental open issue addressed widely by scientists. On the other hand, looking for new states of exotic nature is a central component for theoretical and experimental efforts from electron-positron machine and electron accelerator with fixed target to heavy ion and electron-ion colliders. In this article we present a succinct short overview of the attempt to search for exotic narrow N^∗ and Z states containing light quarks only or also charm, and its connotation for bottom regions (the latter two are also known as P_c (Z_c) and P_b (Z_b) states, respectively in the literature). We address the effort of searching for exotic narrow N^∗ and Z states in light quark sector. We focus on recent progress in searching for signal of P_c and Z_c states photoproduction and its implication into the P_b and Z_b photoproduction and their decay properties. We also discuss future perspectives for the field in electron-ion colliders, a good place to disentangle the nature of some of these states and investigate some other enlightening topics including QCD trace anomaly and quarkonium-nucleon scattering length.

Graphical abstract

Keywords

exotic states / photo- and electro-production / electron-ion colliders / hadron

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Acknowledgements

The accomplishment of this document has benefitted from input from many members of the EicC community, with special thanks to Kuang-Da Chao, Ling-Yun Dai, Feng-Kun Guo, Yu-Tie Liang, Qin-Yong Lin, Xiang Liu, Peng Sun, Jia-Jun Wu, Ju-Jun Xie, Ya-Ping Xie, De-Liang Yao, Zhi Yang, Zhiwen Zhao and Bing-Song Zou. It is grateful to Horst Lenske for collaboration in Section 3 and a proofreading throughout the manuscript. This work was supported by the National Natural Science Foundation of China (Grants Nos. 12075289 and U2032109) and the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB34030301).

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