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arXiv · 2107.14182

X(6200) as a compact tetraquark in the QCD string model

A. V. Nefediev
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Abstract

Recently the LHCb Collaboration announced the first observation of nontrivial structures in the double-$J/\psi$ mass spectrum in the mass range 6.2-7.2 GeV, and a theoretical coupled-channel analysis of these data performed in Phys. Rev. Lett. 126, 132001 (2021) evidenced the existence of a new state $X(6200)$ close to the double-$J/\psi$ 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 $cc\bar{c}\bar{c}$ state bound by QCD forces just below the double-$J/\psi$ threshold. A nontrivial interplay of the quark dynamics associated with this compact state and the molecular dynamics provided by soft gluon exchanges between $J/\psi$ 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.

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A. V. Nefediev. 2021-07-29. X(6200) as a compact tetraquark in the QCD string model. https://doi.org/10.1140/epjc%2Fs10052-021-09511-z

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