Scalar fully-heavy tetraquark states QQ^prime {bar{Q}} bar{Q^prime } in QCD sum rules

Bo-Cheng Yang,Cong-Feng Qiao,Liang Tang

doi:10.1140/epjc/s10052-021-09096-7

Bo-Cheng Yang, Cong-Feng Qiao + Show 1 more

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https://doi.org/10.1140/epjc/s10052-021-09096-7

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Abstract

Very recently, the LHCb Collaboration observed distinct structures with the cc{bar{c}}{bar{c}} in the J/Psi -pair mass spectrum. In this work, we construct four scalar (J^{PC} = 0^{++}) [8_c]_{Qbar{Q^prime }}otimes [8_c]_{Q^prime {bar{Q}}} type currents to investigate the fully-heavy tetraquark state Q Q^prime {bar{Q}} bar{Q^prime } in the framework of QCD sum rules, where Q=c, b and Q^prime = c, b. Our results suggest that the broad structure around 6.2-6.8 GeV can be interpreted as the 0^{++} octet–octet tetraquark states with masses 6.44pm 0.11 GeV and 6.52pm 0.10 GeV, and the narrow structure around 6.9 GeV can be interpreted as the 0^{++} octet–octet tetraquark states with masses 6.87pm 0.11 GeV and 6.96pm 0.11 GeV, respectively. Extending to the b-quark sector,the masses of their fully-bottom partners are found to be around 18.38-18.59 GeV. Additionally, we also analyze the spectra of the [8_c]_{c{bar{c}}}otimes [8_c]_{b {bar{b}}} and [8_c]_{c{bar{b}}}otimes [8_c]_{b {bar{c}}} tetraquark states, which lie in the range of 12.51–12.74 GeV and 12.49–12.81 GeV, respectively.

Highlights

Hadrons with more than the minimal quark content was proposed by Gell-Mann [1] and Zweig [2] in 1964, which were named as multiquark exotic states and were allowed by Quantum Chromodynamics (QCD)
As early as in 1981, the exotic hadrons composed of cccchave been systematically studied in quark–gluon model by Chao for the first time [9], where their masses were predicted to lie in the range 6.4–6.8 GeV and were all above the threshold of two charmonia
The LHCb Collaboration reported their discovery of resonance-like structure in the di-J/ mass spectrum, which opens a whole new arena for multiquark exotic hadron

Summary

Introduction

Hadrons with more than the minimal quark content (qqor qqq) was proposed by Gell-Mann [1] and Zweig [2] in 1964, which were named as multiquark exotic states and were allowed by Quantum Chromodynamics (QCD). We endeavor to analyze in the framework of QCD sum rules whether there exists stable J PC = 0++ tetraquark states with color octet–octet configuration or not, and compare the results with the abovementioned new structures reported by the LHCb Collaboratoin. The last part is left for conclusions and discussion of the results

Formalism

Numerical evaluation

Conclusions