Discovery of the Doubly Charmed Ξcc Baryon Implies a Stable bb(u)over-bar(d)over-bar Tetraquark

Recently, the LHCb Collaboration discovered the first doubly charmed baryon Xi(++)(cc) = ccu at 3621.40 +/- 0.78 MeV, very close to our theoretical prediction. We use the same methods to predict a doubly bottom tetraquark T(bb (u) over bar(d) over bar) with J(P) = 1(+) at 10 389 +/- 12 MeV, 215 MeV below the B- (B) over bar*(0) threshold and 170 MeV below the threshold for decay to B-(B) over bar (0)gamma. The T(bb (u) over bar(d) over bar) is therefore stable under strong and electromagnetic interactions and can only decay weakly, the first exotic hadron with such a property. On the other hand, the mass of T(cc (u) over bar(d) over bar) with J(P) = 1(+) is predicted to be 3882 +/- 12 MeV, 7 MeV, above the (DD)-D-0*(+) threshold and 148 MeVabove the (DD+)-D-0 gamma threshold. T(bc (u) over bar(d) over bar) with J(P) = 0(+) is predicted at 7134 +/- 13 MeV, 11 MeV below the (B) over bar D-0(0) threshold. Our precision is not sufficient to determine whether bc (u) over bar(d) over bar is actually above or below the threshold. It could manifest itself as a narrow resonance just at threshold.