We discuss the possible existence of the fullyheavy tetraquarks. We calculate the ground-state energy of the bbbb bound state, where b stands for the bottom quark, in a nonrelativistic effective field theory framework with onegluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state bbbb tetraquark mass is predicted to be (18.72 ± 0.02) GeV. Mass inequality relations among the lowest Q QQQ states, where Q ∈ {c, b}, and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state Q QQQ. The possible decays of the lowest bbbb are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.

With Gaussian expansion method (GEM), realistic wave functions are used to calculate coupledchannel effects for the bottomonium under the framework of 3 P 0 model. The simplicity and accuracy of GEM are explained. We calculate the mass shifts, probabilities of the B meson continuum, S − D mixing angles, strong and dielectric decay widths. Our calculation shows that both S − D mixing and the B meson continuum can contribute to the suppression of the vector meson's dielectric decay width. We suggest more precise measurements on the radiative decays of Υ(10580) and Υ(11020) to distinguish these two effects. The above quantities are also calculated with simple harmonic oscillator (SHO) wave function approximation for comparison. The deviation between GEM and SHO indicates that it is essential to treat the wave functions accurately for near threshold states.