Spectrum of the S-wave fully-heavy tetraquark states

TL;DR

This study systematically investigates the spectrum of fully-heavy S-wave tetraquark states using a nonrelativistic quark model, providing insights into their possible masses and interpretations of recent experimental states.

Contribution

It introduces a comprehensive calculation of fully-heavy tetraquark spectra considering instanton-induced and one-gluon-exchange interactions, offering new interpretations for observed exotic states.

Findings

$ccar{c}ar{c}$ states around 6500 MeV; $bbar{b}ar{b}$ around 19200 MeV

The $X(6900)$ is likely an excited state, not the ground state

The $X(6600)$ can be a ground $ccar{c}ar{c}$ with $J^{PC}=0^{++}$

Abstract

In present work, spectrum of the $S$-wave fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q=c,b$), i.e., $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$, $bc\bar{c}\bar{c}$/ $cc\bar{b}\bar{c}$, $bb\bar{c}\bar{b}$/$cb\bar{b}\bar{b}$, and $bc\bar{b}\bar{c}$ are systematically investigated within an nonrelativistic constituent quark model, in which the Instanton-induced and one-gluon-exchange interactions are taken into account as the residual spin-dependent hyperfine interaction. Our results show that the states with $cc\bar{c}\bar{c}$ and $bb\bar{b}\bar{b}$ components could be located around $ 6500$ MeV and $ 19200$ MeV, respectively. Based on our calculations, the new $X(6900)$ state observed by LHCb may be not a ground $cc\bar{c}\bar{c}$ tetraquark state, while it could be an orbitally or radially excited state of $cc\bar{c}\bar{c}$ system. On the other hand, the recently reported $X(6600)$ state by CMS and ATLAS can be explained as a ground $cc\bar{c}\bar{c}$ tetraquark state with spin-parity $J^{PC} =0^{++}$.