How good is the factorization approach in charm decays?

An analysis of the factorization approach in charm hadronic decays is carried out by using the spectral-functions method and by exploiting the updated information on the semileptonic processes of both the $D$ meson and the $\tau$ lepton. Not only the two-body but also the multiparticle exclusive decays can be computed for the first time. While for some channels agreement with experiment is somewhat acceptable, within a factor of 2, much larger variance is found for other modes: $D^0\to K^{-}{a}_1^{+}\mathrm{}\left(1260\right)\mathrm{}$ $D^0\to K^{-*}{\pi }^{+}$, $D^0\to K^{-}\pi \pi \pi \pi$.