Relativistic description of heavy tetraquarks

The masses of heavy tetraquarks with hidden charm and bottom are calculated in the framework of the relativistic quark model. The tetraquark is considered as the bound state of a heavy-light diquark and antidiquark. The light quark in a heavy-light diquark is treated completely relativistically. The internal structure of the diquark is taken into account by calculating the diquark-gluon form factor in terms of the diquark wave functions. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that the X(3872) can be the tetraquark state with hidden charm. The masses of ground state tetraquarks with hidden bottom are found to be below the open bottom threshold. Recently, signicant progress in experimental investigations of charmonium spectroscopy has been achieved. Several new states X(3872), Z(3931), Y (3943), X(3943), Y (4260) were observed [1] which provide challenge to the theory, since not all of them can be easily accommodated as the cc-charmonium. The most natural conjecture is that these states are the multiquark composite systems considered long ago e.g. in [2]. Currently the best established state is th