Lessons from weak decays of heavy quarks

Recent experimental results on D-, F- and B-decays are interpreted on the basis of the valence quark model. Transition form factors of currents from heavy mesons to much lighter ones are calculated using relativistic wave functions. The semileptonic decay spectra are mainly determined by a few exclusive channels. The detection of the decay mode B- → ρ0e-antiν will be essential for obtaining |Vub/Vcb|. For nonleptonic decays generally good results are obtained using factorization with little direct annihilation. Small bare amplitudes can be fed by stronger amplitudes through channel mixing caused by strong interaction, an effect which possibly simulates in some instance a direct weak annihilation process. To some extent this proposition can be tested in F+-decays. 22 refs