The spectra of bcb̄c̄ tetraquark states from a diquark-antidiquark perspective

Within the diquark-antidiquark framework, this study investigates the masses of ground-state tetraquarks composed of heavy charm (c) and bottom (b) quarks and antiquarks, using the Bethe-Salpeter formalism. We establish the Bethe-Salpeter equations for the fully heavy bcb̄c̄ tetraquarks to the leading order in 1/mQ expansion. These equations are subsequently solved numerically under the covariant instantaneous approximation with kernels containing scalar confinement and one-gluon exchange terms. Our results show that the spectra of all possible S-wave tetraquark states are above the corresponding two lowest meson decay thresholds via the quark rearrangement. This implies that the ground bcb̄c̄ tetraquark states should be broad.