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 $QQ\bar{q}\bar{q}$ tetraquarks to Hydrogen atom within Quantum chromodynamics (QCD) 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.