Mass spectra of doubly heavy baryons in the relativistic quark model

Mass spectra of baryons consisting of two heavy $(b$ or $c)$ and one light quark are calculated in the framework of the relativistic quark model. The light-quark--heavy-diquark structure of the baryon is assumed. Under this assumption the ground and excited states of both the diquark and quark-diquark bound system are considered. The quark-diquark potential is constructed. The light quark is treated completely relativistically, while the expansion in the inverse heavy quark mass is used revealing the close similarity with the mass spectra of B and D mesons. We find that the relativistic treatment of the light quark plays an important role. The level inversion of the p-wave excitations of the light quark in doubly heavy baryons is discussed.