Resonance X (7300): excited 2S tetraquark or hadronic molecule χc1χc1?

We explore the first radial excitation X-4c(& lowast;) of the fully charmed diquark-antidiquark state X-4c=cccc built of axial-vector components, and the hadronic molecule M=chi c1 chi c1. The masses and current couplings of these scalar states are calculated in the context of the QCD two-point sum rule approach. The full widths of X-4c(& lowast;) and M are evaluated by taking into account their kinematically allowed decay channels. We find partial widths of these processes using the strong couplings g(i )(& lowast;)and G(i)((& lowast;)) at the X-4c(& lowast;)(M )-conventional mesons vertices computed by means of the QCD three-point sum rule method. The predictions obtained for the parameters m=(7235 +/- 75) MeV, Gamma=(144 +/- 18) MeV and m=(7180 +/- 120) MeV, Gamma=(169 +/- 21) MeV of these structures, are compared with the experimental data of the CMS and ATLAS Collaborations. In accordance to these results, within existing errors of measurements and uncertainties of the theoretical calculations, both the excited tetraquark and hadronic molecule may be considered as candidates to the resonance X(7300). Detailed analysis, however, demonstrates that the preferable model for X(7300) is an admixture of the molecule M and sizeable part of X-4c(& lowast;).

Automated summary

In this article, we explore the first radial excitation X-4c(& lowast;) of the fully charmed diquark-antidiquark state X-4c=cccc built of axial-vector components, and the hadronic molecule M=chi c1 chi c1. The masses and current couplings of these scalar states are calculated using the QCD two-point sum rule approach, and their full widths are evaluated by considering their kinematically allowed decay channels. Partial widths of these processes are found using the strong couplings g(i )(& lowast;) and G(i)(& lowast;) at the X-4c(& lowast;)(M)-conventional mesons vertices computed by means of the QCD three-point sum rule method. The obtained predictions for the parameters m=(7235 +/- 75) MeV, Gamma=(144 +/- 18) MeV and m=(7180 +/- 120) MeV, Gamma=(169 +/- 21) MeV of these structures are compared with experimental data, suggesting that both the excited tetraquark and hadronic molecule can be considered as candidates for the resonance X(7300). However, detailed analysis demonstrates that the preferable model for X(7300) is a hybrid involving the molecule M and a substantial part of X-4c(& lowast;).