The heavy tetra-quark states after the discovery of tetra-charm states
This paper is devoted to the study of exclusive charm and bottom aggregates which are suitable, at least partially, for a non-relativistic description. Starting from a simple choice of quarkonia and tetra-quark wave functions we study their production cross sections, total widths and more interesting decay properties. In particular, we compute the production cross sections of the ground state scalar quarkonia getting results compatible with the values appearing in the literature. We also compute the production cross sections of the lower energy states of the charm and bottom tetra-quarks, their decay widths and the decay rates in two $\mu\bar\mu$ pairs and in the $q\bar q\mu\bar\mu$ channel. Our results on the tetra-charm are consistent with the data published by the LHCb Collaboration and those on the tetra-bottom show a reasonable agreement with the indications published by the CMS Collaboration. Our cross section analyses are based on interpolations based on the gluon-gluon luminosity grids published by the NNPDF and CTEQ Collaborations. The hard amplitude calculations are based on QCD in the tree approximation. We think that a careful improvement of our method and a refinement of the experimental data after the foreseen luminosity increase at the LHC will make possible valuable tests of QCD at the intermediate energies.