Systematic studies of DDKK and D(D)over-bar K(K)over-bar four-hadron molecules

Assuming that D-s0(*) (2317) is a DK molecular state with a binding energy of 45 MeV, we investigate the existence of four-hadron molecules, DDKK and D (D) over bar K (K) over bar, with the Gaussian expansion method. Their binding energies are 138-155 MeVand 123-163 MeV below the mass thresholds of DDKK and D (D) over bar K (K) over bar. The D (D) over bar K (K) over bar state has a decay width of 74-107MeV due to the complex K (K) over bar interaction. Further theoretical studies of and experimental searches for such four-hadron molecules can help deepen the understanding of the nonperturbative strong interaction in a nontrivial way.