The QCD factorization in $B \to DKK$ decays
A study of hadron pair production mechanism is motivated by the recent observed decays $\bar B^0\to D^{(*)+}K^-K^0$. One novel phenomenon is threshold enhancement of the kaon pair production. We show that these decays in the heavy quark mass limit can be factorized into a generalized form. The new non-perturbative quantity is the generalized distribution amplitude which describes how a quark-antiquark pair transmits into the hadron pair. A proof of factorization of $\bar B^0\to D^{(*)+}K^-K^0$ decays to all-orders is performed by using the soft-collinear effective theory. The phenomenological application is discussed in brief.