Hunting for exotic doubly hidden-charm/bottom tetraquark states

TL;DR

This paper uses a QCD sum rule method to predict the masses of exotic doubly hidden-charm and bottom tetraquark states, indicating their dominant decay modes and suggesting experimental search channels.

Contribution

It introduces an augmented moment QCD sum rule approach with inequalities to study heavy-quark tetraquarks, providing mass spectra predictions for various quantum states.

Findings

Hidden-charm tetraquark masses are above charmonium thresholds, favoring decay into charmonium pairs.

Hidden-bottom tetraquark masses are below or near bottomonium thresholds, implying potential stability.

Suggested experimental channels include $J/\psi J/\psi$ and $\eta_c \eta_c$ for doubly hidden-charm states.

Abstract

We develop a moment QCD sum rule method augmented by fundamental inequalities to study the existence of exotic doubly hidden-charm/bottom tetraquark states made of four heavy quarks. Using the compact diquark-antidiquark configuration, we calculate the mass spectra of these tetraquark states. There are 18 hidden-charm $cc\bar c\bar c$ tetraquark currents with $J^{PC} = 0^{++}$, $0^{-+}$, $0^{--}$, $1^{++}$, $1^{+-}$, $1^{-+}$, $1^{--}$, and $2^{++}$. We use them to perform QCD sum rule analyses, and the obtained masses are all higher than the spontaneous dissociation thresholds of two charmonium mesons, which are thus their dominant decay modes. The masses of the corresponding hidden-bottom $bb\bar b\bar b$ tetraquarks are all below or very close to the thresholds of the $\Upsilon(1S)\Upsilon(1S)$ and $\eta_b(1S)\eta_b(1S)$, except one current of $J^{PC}=0^{++}$. Hence, we suggest to search for the doubly hidden-charm states in the $J/\psi J/\psi$ and $\eta_c(1S)\eta_c(1S)$ channels.