Gluon enhancements in charmed-meson decays

We address tests of nonspectator diagrams in charmed-meson decays. In particular, we explore the consequences of a model in which such diagrams are enhanced by the emission of a single gluon. For a lifetime ratio $\frac{\tau \left(D^{+}\right)}{\tau \left(D^0\right)}=5\mathrm{}$, we predict (i) $\frac{\tau \left(F^{+}\right)}{\tau \left(D^{+}\right)}\simeq 0.6$, (ii) an enhanced $\Delta S=0\mathrm{}$ rate for $D^{+}$, (iii) a substantial multipion branching fraction for the $F^{+}$, (iv) an $F^{+}\to {\tau }^{+}\nu$ branching fraction of order 10-20%, and (v) restrictive bounds on the $D^0\to {\overline{K}}^0{\pi }^0$ mode.