Flavour symmetries and B decays into a light vector meson

Summary

Heavy-quark (m _Q→∞) flavour symmetry can be used together with the light-quarkSU(3) flavour symmetry to relate the semi-leptonic decays B → ρℓ⥉_ℓ and D → K^*ℓν_ℓ. We use recent data on the semi-leptonic D decays to make predictions on the B→ϱ transition. We also compare these predictions with other theoretical approaches and we show that, in order to discriminate among the different models, a measurement of the ϱ polarization would be useful. Heavyflavour symmetry can also be used to relate the decay processes D → K^*ℓν_ℓ and B→K^*γ, in the limitm _Q→∞. We compare these predictions with the CLEO II data and we argue that a satisfactory agreement is found only if a consistent treatment of theO(1/m _Q) corrections is performed.