Exclusive nonleptonic decays

Constraints on quark diagrams for exclusive decays from group theory are investigated. In contrast to previous statements, we find a one-to-one correspondence between reduced matrix elements of flavor symmetry (SU3) and the ''naive'' quark diagrams of the spectator and annihilation type. In Cabibbo suppressed decays however, group theory relates penguin and annihilation (W-exchange) diagrams, consequently ruling out models with spectator dominance and large penguins. These results are expected to be more general, having as yet been illustrated for two-body decays of charmed mesons