Tetraquark state candidates: $Y(4140)$, $Y(4274)$ and $X(4350)$

Understand

In this article, we tentatively assign the $Y(4140)$, $Y(4274)$ and $X(4350)$ to be the scalar and tensor $cs\bar{c}\bar{s}$ tetraquark states, respectively, and study them with the QCD sum rules.

• In the operator product expansion, we take into account the vacuum condensates up to dimension-10.
• In calculations, we use the formula $\mu=\sqrt{M^2_{X/Y/Z}-(2{\mathbb{M}}_c)^2}$ to determine the energy scales of the QCD spectral densities.
• The numerical results favor assigning the $Y(4140)$ to be the $J^{PC}=2^{++}$ diquark-antidiquark type tetraquark state, and disfavor assigning the $Y(4274)$ and $X(4350)$ to be the $0^{++}$ or $2^{++}$ tetraquark states.