Abstract
Masses of the ground-state teraquarks composed from heavy $c$ and $b$ quarks and antiquarks are calculated in the diquark-antidiquark picture in the framework of the relativistic quark model based on the quasipotential approach. The quasipotentials of the quark-quark and diquark-antidiquark interactions are constructed similarly to the previous consideration of mesons and baryons. It is assumed that the diquark and antidiquark interact in the tetraquark as a whole and the internal structure of the diquarks is taken into account. All such tetraquarks are found above the thresholds of decays to two heavy quarkonia. This is a result of the consideration of the diquark not to be a point-like object. Therefore such tetraquarks can be observed as broad structures decaying dominantly to quarkonia. The broad structure next to the di-$J/\psi$ mass threshold, recently observed by the LHCb Collaboration, can correspond to the ground $2^{++}$-state tetraquark consisting of four charm quarks.
Highlights
Theoretical and experimental investigations of the properties of exotic hadrons have attracted substantial interest, especially in last two decades
Significantly different interpretations for the qqqqcandidates were proposed: molecules composed from two mesons loosely bound by the meson exchange, compact tetraquarks composed of a diquark and antidiquark bound by strong forces, hadroquarkonia composed of a heavy quarkonium embedded in a light meson, kinematic cusps, etc
It is important to point out that diquarks and antidiquarks are not the pointlike objects. Their shortdistance interaction with gluons is smeared by the form factors which are calculated in terms of the overlap integrals of the diquark wave functions
Summary
Theoretical and experimental investigations of the properties of exotic hadrons have attracted substantial interest, especially in last two decades This subject became a hot topic since the first explicit experimental evidence of the existence of hadrons with compositions different from the usual qqfor mesons and qqq for baryons became available Their shortdistance interaction with gluons is smeared by the form factors which are calculated in terms of the overlap integrals of the diquark wave functions Such an approach was previously applied for the calculation of the masses of heavy (qQqQ , QQqq , Qqqq ) and light (qqqq ) tetraquarks [16,17,18,19,20].
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