Open charm and bottom tetraquarks in an extended relativized quark model

In this work we systematically calculate the mass spectra of open charm and bottom tetraquarks qq (q) over bar (Q) over bar within an extended relativized quark model. The four-body relativized Hamiltonians including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved by using the variational method. We find that the predicted masses of four 0(+) ud (s) over bar (c) over bar states are 2765, 3065, 3152, and 3396 MeV, which disfavor the assignment of the newly observed X-0(2900) as a compact tetraquark. Moreover, the mass spectra of the open charm and bottom tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. In addition, our results suggest that the flavor-exotic states nn (s) over bar (c) over bar, nn (s) over bar (b) over bar, ss (n) over bar (c) over bar, and ss (n) over bar (b) over bar and their antiparticles can be searched for in the heavy-light meson plus kaon fmal states by future experiments. More theoretical and experimental efforts are needed to investigate these singly heavy tetraquarks.