Tetraquark candidates in LHCb's di-J/ψ mass spectrum

In this article,we study the first radial excited states of the scalar,axialvector,vector,and tensor diquark-antidiquark-type cccc tetraquark states with the QCD sum rules and obtain the masses and pole residues;then,we use the Regge trajectories to obtain the masses of the second radial excited states.The predicted masses support assigning the broad structure from 6.2 to 6.8 GeV in the di-J/ψ mass spectrum to be the first radial excited state of the scalar,axialvector,vector,or tensor cccc tetraquark state,as well as assigning the narrow structure at about 6.9 GeV in the di-J/ψ mass spectrum to be the second radial excited state of the scalar or axialvector cccc tetraquark state.