Interpretations of the X(3872) and its production at hadron colliders

Among the discovered new hadron XYZ states, the X(3872) might be the most elusive one. In this talk, I will briefly review the possible explanations of X(3872), and put stress on its production at hadron colliders. Based on the calculation in nonrelativistic QCD, we argue that a substantial $\chi_{c1}(2P)$ component is needed to explain the large production rates of X(3872) at the Tevatron and LHC. And this is also supported by the observed large decay branching fraction of X(3872) to $\psi(2S)\gamma$, as well as the large production rate of X(3872) in B meson decays.