Gluonic Tetracharm Configuration of $X(6900)$

TL;DR

This paper proposes that the newly observed $X(6900)$ structure is a gluonic tetracharm hybrid state, using QCD Sum Rule calculations, and predicts related tetraquark and tetrabottom states for future experimental verification.

Contribution

It introduces a hybrid interpretation for $X(6900)$ as a gluonic tetracharm state and performs mass spectrum calculations to support this hypothesis.

Findings

$X(6900)$ could be a gluonic tetracharm hybrid state.

Predicted a structure around 7.2 GeV with different quantum numbers.

Forecasted tetrabottom hybrid states for future experiments.

Abstract

Recently, a new hadronic structure at around $6.9$ GeV was observed in an LHCb experiment. From its limited yet known decay mode, one could still determine that it contains at least four charm quarks and hence belongs to the category of exotic state. This finding indicates for the first time the tetracharm exotic states and is therefore quite importance. In this letter, we propose a nature hybrid interpretation for the structure of $X(6900)$, i.e. in $[\bar{3}_c]_{c c}\otimes[8_c]_{G}\otimes[3_c]_{\bar{c} \bar{c}}$ configuration with $J^{PC}=0^{++}$, and by using the QCD Sum Rule technique we performed mass spectrum calculation. The results showed that the observed $X(6900)$ could be a gluonic tetracharm state, and some other structures may exist, e.g., one around $7.2$ GeV in the tetracharm hybrid configuration and with $J^{PC}=0^{-+}$. We also predict the tetrabottom hybrid states, leaving for future experiment.