Diquark-antidiquark states with hidden or open charm and the nature ofX(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 $c\overline{c}$ 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 $X^{\pm }$ in the weak decays of $B^{+,0}$.