Heavy tetraquarks in the hyperspherical approach

Within the quark model and hyperspherical method, the bound states of four heavy quarks and antiquarks (tetraquarks) are investigated. In hyperradial approximation, the Schroedinger equation is reduced to a one-dimensional equation after averaging over angles in hyperspace. This equation is solved numerically and analytically within the variational method. The hyperfine structure of the spectrum is calculated. To increase the accuracy of the calculation, corrections to the energy levels from the QCD generalization of the Breit Hamiltonian are taken into account.