Nonfactorizable Amplitudes in Weak Nonleptonic Decays of Heavy Mesons
  We discuss nonfactorizable $1/N_c$ contributions in the amplitudes of non-leptonic exclusive decays of the type $B\rightarrow D\pi$ ($N_c$ is the number of colors). In a certain kinematical limit rather reliable estimates are possible. It is demonstrated that the nonfactorizable parts are of the same order as the factorizable $1/N_c$ parts of the ampiltudes, and have the opposite sign. Thus, an approximate rule of discarding $1/N_c$ corrections in the nonleptonic exclusive decays emerges dynamically. It is shown that this rule is not exact and the degree of compensation is different in different channels.   Our predictions make use of the fact that a key matrix element that measures deviations from factorization can be determined using the heavy quark effective theory. 
B. Blok and M. Shifman