Nonfactorizable soft gluons in nonleptonic heavy meson decays

We include nonfactorizable soft gluon corrections into the perturbative QCD formalism for exclusive nonleptonic heavy meson decays, which combines factorization theorems and effective field theory. These corrections are classified according to their color structures, and exponentiated separately to complete the Sudakov resummation up to next-to-leading logarithms. The nonfactorizable contributions in nonleptonic decays are clearly identified in our formalism, and found to be positive for bottom decays and negative for charm decays. Our analysis confirms that the large-Nc approximaton is applicable to charm decays, but not to bottom decays, consistent with the phenomenological implications of experimental data. The comparision of our predictions with those from QCD sum rules is also made.