X(5568) as a $su \bar d \bar b$ tetraquark in a simple quark model

The $S$-wave eigenstates of tetraquarks of type $s u \bar d \bar b$ with J$^{P}$ = 0$^{+}$, 1$^{+}$ and 2$^{+}$
are studied within a simple quark model with
chromomagnetic interaction and effective quark masses extracted
from meson and baryon spectra.
It is tempting to see if this spectrum can accommodate the new narrow structure X(5568),
observed by the D\O~~Collaboration, but not confirmed by the LHCb Collaboration.
If it exists, such a tetraquark is a system with four different flavors
and its study can improve our understanding of multiquark systems.
The presently calculated mass of X(5568) agrees quite well with the experimental value of
he D\O~~Collaboration. Predictions are also made for the spectrum of the charmed partner $s u \bar d \bar c$.
However we are aware of the
difficulty of extracting effective quark masses, from mesons and baryons,
to be used in multiquark systems.