Analysis of Zcs (3985) as the axialvector tetraquark state * *Supported by National Natural Science Foundation of China (11775079)

Zhi-Gang Wang

doi:10.1088/1674-1137/abfa83

Abstract

In this study, we choose the scalar and axialvector diquark operators in the color antitriplet as the fundamental building blocks to construct four-quark currents and investigate the diquark-antidiquark type axialvector tetraquark states in the framework of the QCD sum rules. The predicted tetraquark mass is in excellent agreement with the experimental value from the BESIII collaboration, which supports identifying as the cousin of with quantum numbers . We take into account the light flavor mass-breaking effect to estimate the mass spectrum of the diquark-antidiquark type hidden-charm tetraquark states with strangeness according to previous studies.

Highlights

Very recently, the BESIII collaboration observed an excess over the known contributions of the conventional charmed mesons near the Ds−D∗0 and Ds∗−D0 mass thresholds in the K+ recoil-mass spectrum with the significance of 5.3 σ in the processes of the e+e− → K+(Ds−D∗0 + Ds∗−D0) [1]
We tentatively identify the Zc−s(3985) as the diquarkantidiquark type axialvector tetraquark state with the four valence quarks ccsuand examine its mass in the framework of the QCD sum rules at length
We choose the scalar and axialvector diquark operators and antidiquark operators as the fundamental building blocks to construct the fourquark currents and investigate the diquark-antidiquark type axialvector tetraquark states ccuswith the QCD sum rules in the condition that we accomplish the operator product expansion up to the vacuum condensates of dimension 10 consistently based on our reasonable analysis and successful experience, and apply the energy scale formula μ = MZ − (2Mc)2 using the effective

Summary

Introduction

The BESIII collaboration observed an excess over the known contributions of the conventional charmed mesons near the Ds−D∗0 and Ds∗−D0 mass thresholds in the K+ recoil-mass spectrum with the significance of 5.3 σ in the processes of the e+e− → K+(Ds−D∗0 + Ds∗−D0) [1] It is the first candidate of the charged hidden-charm tetraquark state with strangeness. In Ref.[21], we take the diquark and antidiquark operators in the color antitriplet and color triplet respectively as the fundamental building blocks to construct the scalar, axialvector and tensor four-quark local currents to investigate the mass spectrum of the ground state tetraquark states with hidden-charm but without strangeness in the framework of the QCD. We tentatively identify the Zc−s(3985) as the diquarkantidiquark type axialvector tetraquark state with the four valence quarks ccsuand examine its mass in the framework of the QCD sum rules at length.

The QCD sum rules for the axialvector tetraquark states with strangeness

Numerical results and discussions

Conclusion