Masses of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Q</mml:mi><mml:mi>Q</mml:mi><mml:mover accent="true"><mml:mi>Q</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover><mml:mover accent="true"><mml:mi>Q</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:math> tetraquarks in the relativistic diquark–antidiquark picture
R. N. Faustov, V. O. Galkin, E. M. Savchenko
Abstract
Masses of the ground-state tetraquarks 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 pointlike object. Therefore, such tetraquarks can be observed as broad structures decaying dominantly to quarkonia. The broad structure next to the di-$J/\ensuremath{\psi}$ mass threshold, recently observed by the LHCb Collaboration, can correspond to the ground ${2}^{++}$-state tetraquark consisting of four charm quarks.