X(5568) as a sud̄b̄ tetraquark in a simple quark model

The S -wave eigenstates of tetraquarks of type 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 DØ 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 the DØ Collaboration. Predictions are also made for the spectrum of the charmed partner . However we are aware of the difficulty of extracting effective quark masses, from mesons and baryons, to be used in multiquark systems.