Exotic hadrons from scattering in the diabatic dynamical diquark model

The diabatic framework generalizes the adiabatic approximation built into the Born-Oppenheimer (BO) formalism and is devised to rigorously incorporate the mixing of BO-approximation eigenstates with two-particle thresholds. We recently applied this framework in a bound-state approximation to the mixing of hidden-charm dynamical-diquark tetraquark states with open-charm dimeson thresholds. Since almost all of these states are observed as above-threshold resonances, we here implement the corresponding scattering formalism to allow for a study of exotic tetraquark resonances within the diabatic framework. We calculate elastic open-charm dimeson cross sections (in channels with zero, open, and hidden strangeness) as functions of center-of-mass energy and observe the development of true resonances, near resonances, and various threshold cusp effects. As an example, χc1(3872) can originate in the 1++ channel as a diquark-antidiquark state enhanced by the D0D¯∗0 threshold, with or without an additional contribution from the conventional charmonium χc1(2P) state.