Reanalysis of the $Y(3940)$, $Y(4140)$, $Z_c(4020)$, $Z_c(4025)$ and $Z_b(10650)$ as molecular states with QCD sum rules

Abstract: In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the $J^{PC}=0^{++}$, $1^{+-}$, $2^{++}$ $D^\bar{D}^$, $D_s^\bar{D}_s^$, $B^\bar{B}^$, $B_s^\bar{B}_s^$ molecular states with the QCD sum rules. In calculations, we use the formula $\mu=\sqrt{M^2_{X/Y/Z}-(2{\mathbb{M}}_Q)^2}$ to determine the energy scales of the QCD spectral densities. The numerical results favor assigning the $Z_c(4020)$ and $Z_c(4025)$ as the $J^{PC}=0^{++}$, $1^{+-}$ or $2^{++}$ $D^\bar{D}^$ molecular states, the $Y(4140)$ as the $J^{PC}=0^{++}$ $D^_s{D}_s^$ molecular state, the $Z_b(10650)$ as the $J^{PC}=1^{+-}$ $B^\bar{B}^$ molecular state, and disfavor assigning the $Y(3940)$ as the ($J^{PC}=0^{++}$) molecular state. The present predictions can be confronted to the experimental data in the futures.