Hadronic molecules ηcηc and χc0χc0

The fully charmed hadronic scalar molecules M1=eta c eta c and M2=chi c0 chi c0 are studied in the context of the QCD sum rule method. The masses m, m~ and current couplings f, f~ of these states are calculated using the two-point sum rule approach. The obtained results m=(6264 +/- 50)MeV and m~=(6954 +/- 50)MeV are employed to determine their decay channels. It is demonstrated that the processes M1 -> J/psi J/psi and M1 -> eta c eta c are kinematically allowed decay modes of M1. The molecule M2 decays to J/psi J/psi, J/psi psi ', eta c eta c, eta c eta c(2S), eta c chi c1(1P), and chi c0 chi c0 mesons. The partial widths of all these processes are evaluated by means of the three-point sum rule calculations, which are necessary to extract the strong couplings gi at vertices M1J/psi J/psi, M1 eta c eta c, and others. Our estimates for the full widths of the molecules Gamma M1=(320 +/- 72)MeV and Gamma M2=(138 +/- 18)MeV, as well as their masses are compared with parameters of the X resonances discovered by the LHCb-ATLAS-CMS Collaborations in the di-J/psi and J/psi psi ' invariant mass distributions. We argue that the molecule M1 can be considered as a real candidate to the resonance X(6200). The structure M2 may be interpreted as X(6900) or one of its components in combination with a scalar tetraquark.

Automated summary

The fully charmed hadronic scalar molecules M1=eta c eta c and M2=chi c0 chi c0 are studied using the QCD sum rule method. The masses and current couplings of these states are calculated, and their decay channels are determined. The structures M1 and M2 are found to have different decay modes and widths.