Communications in Theoretical Physics ›› 2021, Vol. 73 ›› Issue (12): 125201. doi: 10.1088/1572-9494/ac27a2

• Particle Physics and Quantum Field Theory • Previous Articles     Next Articles

A survey of heavy–heavy hadronic molecules

Xiang-Kun Dong1,2,(),Feng-Kun Guo1,2,(),Bing-Song Zou1,2,3,()   

  1. 1CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
    2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
    3School of Physics, Central South University, Changsha 410083, China
  • Received: 2021-08-06 Revised: 2021-09-16 Accepted: 2021-09-17 Published: 2021-12-01
  • Contact: Xiang-Kun Dong E-mail:dongxiangkun@itp.ac.cn;fkguo@itp.ac.cn;zoubs@itp.ac.cn

Abstract:

The spectrum of hadronic molecules composed of heavy–antiheavy charmed hadrons has been obtained in our previous work. The potentials are constants at the leading order, which are estimated from resonance saturation. The experimental candidates of hadronic molecules, say X(3872), Y(4260), three Pc states and Pcs(4459), fit the spectrum well. The success in describing the pattern of heavy–antiheavy hadronic molecules stimulates us to give more predictions for the heavy–heavy cases, which are less discussed in literature than the heavy–antiheavy ones. Given that the heavy–antiheavy hadronic molecules, several of which have strong experimental evidence, emerge from the dominant constant interaction from resonance saturation, we find that the existence of many heavy–heavy hadronic molecules is natural. Among these predicted heavy–heavy states we highlight the DD* molecule and the ${D}^{(* )}{{\rm{\Sigma }}}_{c}^{(* )}$ molecules, which are the partners of the famous X(3872) and Pc states. Quite recently, LHCb collaboration reported a doubly charmed tetraquark state, Tcc, which is in line with our results for the DD* molecule. With the first experimental signal of this new kind of exotic states, the upcoming update of the LHCb experiment as well as other experiments will provide more chances of observing the heavy–heavy hadronic molecules.

Key words: hadronic molecules, heavy–heavy systems, Bethe–Salpeter equation, constant interaction, resonance saturation