# Light axial-vector and vector resonances $X(2100)$ and $X(2239)$

## TL;DR

This paper models the resonances X(2100) and X(2239) as tetraquarks with specific quark content, predicting their masses and decay widths using QCD sum rule methods, and finds good agreement with experimental data.

## Contribution

It provides the first theoretical predictions of the masses and decay widths of X(2100) and X(2239) as tetraquark states using QCD sum rules, matching recent experimental observations.

## Key findings

- Predicted axial-vector tetraquark mass: 2067 ± 84 MeV.
- Predicted decay width of X(2100): 130.2 ± 30.1 MeV.
- Predicted vector tetraquark mass: 2283 ± 114 MeV.

## Abstract

We study features of the resonances $X(2100)$ and $X(2239)$ by treating them as the axial-vector and vector tetraquarks with the quark content $ss \overline{s}\overline{s}$, respectively. The spectroscopic parameters of these exotic mesons are calculated in the framework of the QCD two-point sum rule method. Obtained prediction for the mass $m=(2067 \pm 84)~\mathrm{MeV}$ of the axial-vector state is in excellent agreement with the mass of the structure $X(2100)$ recently observed by the BESIII Collaboration in the decay $J/\psi \to \phi \eta \eta^{\prime}$ as the resonance in the $\phi \eta^{\prime}$ mass spectrum. We explore also the $S$-wave decays $X(2100) \to \phi\eta^{\prime}$ and $X(2100) \to \phi \eta$ using the QCD light-cone sum rule approach and technical methods of the soft-meson approximation. The width of the axial-vector tetraquark, $\Gamma=(130.2\pm 30.1)~\mathrm{MeV}$, saturated by these two decays is comparable with the measured full width of the resonance $X(2100)$. Our prediction for the vector $ss\overline{s}\overline{s }$ tetraquark's mass $\widetilde{m}=(2283\pm 114)~\mathrm{MeV}$ is consistent with the experimental result $2239.2 \pm 7.1 \pm 11.3~\mathrm{MeV}$ of the BESIII Collaboration for the mass of the resonance $X(2239)$.