Spectroscopy and decays of the fully-heavy tetraquarks

We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the bb b b bound state, where b stands for the bottom quark, in a nonrelativistic effective field theory framework with one-gluon-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 QQQQ states, where Q \c, b\, and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state QQQQ. 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.