Scalar tetraquark state candidates: X(3915), X(4500) and X(4700)

In this article, we tentatively assign the X(3915) and X(4500) to be the ground state and the first radial excited state of the axialvector–diquark–axialvector–antidiquark type scalar csc̄s̄ tetraquark states, respectively, assign the X(4700) to be the ground state vector–diquark–vector–antidiquark type scalar csc̄s̄ tetraquark state, and study their masses and pole residues with the QCD sum rules in detail by calculating the contributions of the vacuum condensates up to dimension 10. The numerical results support assigning the X(3915) and X(4500) to be the ground state and the first radial excited state of the axialvector–diquark–axialvector–antidiquark type scalar csc̄s̄ tetraquark states, respectively, and assigning the X(4700) to be the ground state vector–diquark–vector–antidiquark type scalar csc̄s̄ tetraquark state.