Analysis of the $Z_{cs}(3985)$ as the axialvector tetraquark state

TL;DR

This paper uses QCD sum rules with diquark operators to analyze the $Z_{cs}(3985)$ as an axialvector tetraquark, predicting a mass that matches experimental data and supporting its identification as a cousin of the $Z_c(3900)$.

Contribution

It constructs diquark-antidiquark currents to predict the $Z_{cs}(3985)$ mass, providing theoretical support for its tetraquark nature and quantum numbers.

Findings

Predicted mass $M_Z=3.99 ext{ GeV}$ matches experimental value.

Supports $Z_{cs}(3985)$ as an axialvector tetraquark.

Estimates mass spectrum considering flavor $SU(3)$ breaking.

Abstract

In this paper, we choose the scalar and axialvector diquark operators in the color antitriplet as the fundamental building blocks to construct the four-quark currents and investigate the diquark-antidiquark type axialvector tetraquark states $c\bar{c}u\bar{s}$ in the framework of the QCD sum rules. The predicted tetraquark mass $M_Z=3.99\pm0.09\,\rm{GeV}$ is in excellent agreement with the experimental value $3985.2^{+2.1}_{-2.0}\pm1.7\,\rm{MeV}$ from the BESIII collaboration, which supports identifying the $Z_{cs}(3985)$ as the cousin of the $Z_c(3900)$ with the quantum numbers $J^{PC}=1^{+-}$. We take into account the light flavor $SU(3)$ mass-breaking effect to estimate the mass spectrum of the diquark-antidiquark type hidden-charm tetraquark states having the strangeness according to the previous works.