We consider the predictions of chiral perturbation theory and heavy-quark symmetry for the decays $D\to K\pi \overline{l}{\nu }_l$, $D\to \pi \pi \overline{l}{\nu }_l$, $B\to \pi \pi l{\overline{\nu }}_l$ and $B\to D\pi l{\overline{\nu }}_l(l=e or \mu )$.

• Received 6 April 1992

DOI:https://doi.org/10.1103/PhysRevD.46.5040