Diquark-antidiquark states with hidden or open charm and the nature of X(3872)

Heavy-light diquarks can be the building blocks of a rich spectrum of states which can accommodate some of the newly observed charmoniumlike resonances not fitting a pure cc¯ assignment. We examine this possibility for hidden and open charm diquark-antidiquark states deducing spectra from constituent quark masses and spin-spin interactions. Taking the X(3872) as input we predict the existence of a 2⁺⁺ state that can be associated to the X(3940) observed by Belle and reexamine the state claimed by SELEX, X(2632). The possible assignment of the previously discovered states D_s(2317) and D_s(2457) is discussed. We predict X(3872) to be made of two components with a mass difference related to m_u-m_d and discuss the production of X(3872) and of its charged partner X^± in the weak decays of B^+,0.