Non Leptonic Decays : a Long Story

The large SU(3)F violations in the amplitudes for the D decays into a pair of pseudoscalar mesons are mainly accounted by the final state interaction and by contributions related to the non conservation of the strangeness changing vector currents of the octet. An approximate selection rule for the contributions proportional to V_cbV^∗_ub allows to predict the CP violating asymmetries in terms of only one parameter depending on the penguin contribution. The enhancement of the octet final states with respect to the 27, larger than expected, may be related to the presence of the nonet of scalar mesons with masses around the one of the D's. A similar mechanism may be responsible for the dominance of the ΔI=12 term in K decays related to the large f0 resonance with a mass near to one of the decaying particles.