Hidden-charmonium decays of $Z_c(3900)$ and $Z_c(4025)$ in intermediate meson loops model

Understand

The BESIII collaboration reported an observation of two charged charmonium-like structure $Z_c^{\pm}(3900)$ and $Z_c^{\pm}(4025)$ in $e^+e^- \to (J/\psi \pi)^{\pm} \pi^{\mp}$ and $e^+e^- \to (D^* {\bar D}^*)^{\pm} \pi^{\mp}$ at ${\sqrt s} =4.26$ GeV recently, which could be an analogue of $Z_b(10610)$ and $Z_b(10650)$ claimed by the Belle Collaboration.

• In this work, we investigate the hidden-charmonium transitions of $Z_c^{\pm}(3900)$ and $Z_c^{\pm}(4025)$ via intermediate $D^{(*)} {D}^{(*)}$ meson loops.
• Reasonable results for the branching ratios by taking appropriate values of $\alpha$ in this model can be obtained, which shows that the intermediate $D^{(*)} {D}^{(*)}$ meson loops process may be a possible mechanism in these decays.
• Our results are consistent with the power-counting analysis, and comparable with the calculations in the framework of nonrelativistic effective field theory to some extent.