  Masses of the ground, orbitally and radially excited states of the asymmetric
fully heavy tetraquarks, composed of charm (c) and bottom (b) quarks and
antiquarks are calculated in the relativistic diquark-antidiquark picture. The
relativistic quark model based on the quasipotential approach and quantum
chromodynamics is used to construct the quasipotentials of the quark-quark and
diquark-antidiquark interactions. These quasipotentials consist of the
short-range one-gluon exchange and long-distance linear confinement
interactions. Relativistic effects are consistently taken into account. A
tetraquark is considered as a bound state of a diquark and an antidiquark which
are treated as a spatially extended colored objects and interact as a whole. It
is shown that most of the investigated tetraquarks states (including all ground
states) lie above the fall-apart strong decay thresholds into a meson pair. As
a result they can be observed as wide resonances. Nevertheless, several
orbitally excited states lie slightly above or even below these fall-apart
thresholds, thus they could be narrow states.
