Doubly-charged ${T}_{cc}^{++}$ states in the dynamical diquark model

One of the celebrated tools in explaining the hydrogen atom is Born-Oppenheimer approximation. The resemblance of $QQ\overline{q}\overline{q}$ tetraquarks to hydrogen atom within quantum chromodynamics implies usage of Born-Oppenheimer approximation for these multiquark states. In this work, we use dynamical diquark model to calculate mass spectra and sizes of doubly charmed and charged tetraquark states denoted as ${T}_{cc}^{++}$. Our results for mass spectra indicate some bound-state candidates with respect to corresponding two-meson thresholds. Calculation of expectation values of $\sqrt{⟨{r}^{2}⟩}$ reflects that doubly charmed and charged tetraquark states are compact.