$QQ\bar{Q}\bar{Q}$ states: masses, production, and decays

The question of whether there exist bound states of two heavy quarks $Q=(c,b)$ and antiquarks $\bar{Q}=(\bar{c},\bar{b})$, distinct from a pair of quark-antiquark mesons, has been debated for more than forty years. We suggest some means of producing and observing $Q_1{Q}_2{\bar{Q}}_3{\bar{Q}}_4$ resonant states, concentrating on the $cc\bar{c}\bar{c}$ channel which is most easily produced and the $bb\bar{b}\bar{b}$ channel which has a better chance of being relatively narrow. We obtain $M_{(cc)(\bar{c}\bar{c})}=6,192\pm 25$ MeV and $M_{(bb)(\bar{b}\bar{b})}=18,826\pm 25$ MeV, for the charmed and bottom tetraquarks, respectively. Experimental search for these states in the relevant mass region is highly desirable.