Spectrum of the fully-heavy tetraquark state QQ Q ̄ ′ Q ̄ ′

Abstract

In this work, we systematically calculate the mass spectra of the S-wave fully-heavy tetraquark states, bbb̄b̄, ccc̄c̄, and bbc̄c̄, in two nonrelativistic quark models. A tetraquark state may be an admixture of a 6c-6̄c state and a 3̄c-3c one, where 6c-6̄c(3̄c-3c) denotes the color configuration with a 6c (3̄c) diquark and a 6̄c (3c) antidiquark. For the tetraquark states bbb̄b̄ and ccc̄c̄ with JPC=0++, the 6c-6̄c state is lower than the 3̄c-3c one in both the two quark models, while the order of the bbc̄c̄ states depend on models. The 6c-6̄c and 3̄c-3c mixing effects are induced by the hyperfine interactions between the diquark and antidiquark, while the contributions from the one-gluon-exchange Coulomb or the linear confinement potentials vanish for the QQQ̄′Q̄′ system. With the couple-channel effects, we obtain the similar mass spectra. The numerical results show that the ground QQQ̄′Q̄′ (Q=b, c and Q′=b, c) tetraquark states are located above the corresponding scattering states, which indicates that there may not exist a bound state in the scheme of the two quark models.