Interpretation of $Z_c(4025)$ as the Hidden Charm Tetraquark States via QCD Sum Rules

Abstract

By using QCD Sum Rules, we found that the charged hidden charm tetraquark $[cu][\bar{c}\bar{d}]$ states with $J^P=1^{-}$ and $2^{+}$, which are possible quantum numbers of the newly observed charmonium-like resonance $Z_c(4025)$, have masses of $m_{1^{-}}^c=(4.54\pm 0.20)\text{GeV}$ and $m_{2^{+}}^c=(4.04\pm 0.19)\text{GeV}$. The contributions up to dimension eight in the Operator Product Expansion (OPE) were taken into account in the calculation. The tetraquark mass of $J^P=2^{+}$ state was consistent with the experimental data of $Z_c(4025)$, suggesting the $Z_c(4025)$ state possessing the quantum number of $J^P=2^{+}$. Extending to the b-quark sector, the corresponding tetraquark masses $m_{1^{-}}^b=(10.97\pm 0.25)\text{GeV}$ and $m_{2^{+}}^b=(10.35\pm 0.25)\text{GeV}$ were obtained, which are testable in future B-factories.

Comments: 15 pages, 6 figures, to appear in European Physical Journal C