https://doi.org/10.1140/epjc/s10052-021-09511-z
Regular Article - Theoretical Physics
X(6200) as a compact tetraquark in the QCD string model
1
Moscow Institute of Physics and Technology, Institutsky lane 9, Dolgoprudny, 141700, Moscow Region, Russia
2
P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninskiy Prospect 53, 119991, Moscow, Russia
Received:
16
May
2021
Accepted:
29
July
2021
Published online:
4
August
2021
Recently the LHCb Collaboration announced the first observation of nontrivial structures in the double-
mass spectrum in the mass range 6.2–7.2 GeV, and a theoretical coupled-channel analysis of these data performed in Dong et al. (Phys Rev Lett 126:132001, 2021) evidenced the existence of a new state X(6200) close to the double- threshold. Although its molecular interpretation seems the most plausible assumption, the present data do not exclude an admixture of a compact component in its wave function, for which a fully-charmed compact tetraquark is the most natural candidate. It is argued in this work that the QCD string model is compatible with the existence of a compact 
state bound by QCD forces just below the double- threshold. A nontrivial interplay of the quark dynamics associated with this compact state and the molecular dynamics provided by soft gluon exchanges between mesons is discussed and the physical X(6200) is argued to be a shallow bound state, in agreement with the results of the aforementioned coupled-channel analysis of the LHCb data.
© The Author(s) 2021
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