$D^*\bar D^*$ molecule interpretation of $Z_c(4025)$

TL;DR

This paper uses QCD sum rules to interpret the $Z_c(4025)$ as a $D^*ar D^*$ molecular state, providing a mass estimate consistent with experimental observations and predicting a similar bottomonium state.

Contribution

It is the first QCD sum rule analysis of the $Z_c(4025)$ as a $D^*ar D^*$ molecule, including spectral density calculations up to dimension eight.

Findings

Mass of $Z_c(4025)$ estimated at $4.04 ext{ GeV}$, compatible with experimental data.

Predicted mass of the hidden-bottom $B^*ar B^*$ molecular state at $9.98 ext{ GeV}$.

Abstract

We have used QCD sum rules to study the newly observed charged state $Z_c(4025)$ as a hidden-charm $D^*\bar D^*$ molecular state with the quantum numbers $I^G(J^{P})=1^+(1^{+})$. Using a $D^*\bar D^*$ molecular interpolating current, we have calculated the two-point correlation function and the spectral density up to dimension eight at leading order in $\alpha_s$. The extracted mass is $m_X=(4.04\pm0.24)$ GeV. This result is compatible with the observed mass of $Z_c(4025)$ within the errors, which implies a possible molecule interpretation of this new resonance. We also predict the mass of the corresponding hidden-bottom $B^*\bar B^*$ molecular state: $m_{Z_b}=(9.98\pm0.21)$ GeV.