Spectroscopy and decays of the fully-heavy tetraquarks

We discuss the possible existence of the fullyheavy tetraquarks. We calculate the ground-state energy of the bb (b) over bar(b) over bar 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 QQ (Q) over bar(Q) over bar states, where Q is an element of (c, b), and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state QQ (Q) over bar(Q) over bar. The possible decays of the lowest bb (b) over barb 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.