Evidence for the existence of ud(b)over-bar(b)over-bar and the nonexistence of ss(b)over-bar(b)over-bar and cc(b)over-bar(b)over-bar tetraquarks from lattice QCD

We combine lattice QCD results for the potential of two static antiquarks in the presence of two quarks qq of finite mass and quark model techniques to study possible existing qq (b) over bar(b) over bar tetraquarks within the Born-Oppenheimer approximation. While there is strong indication for a bound four-quark state for qq = (ud - du)/root 2, i.e., isospin I = 0, which is stable with respect to QCD, i.e., can only decay weakly, we find clear evidence against the existence of corresponding tetraquarks with qq is an element of {uu, (ud + du)/root 2, dd}, i.e., isospin I = 1, qq = ss, and qq = cc.