Observation of $\overline{B}\to D^{(\ast )}{\pi }^{+}{\pi }^{-}{\ell }^{-}\overline{\nu }$ decays in $e^{+}{e}^{-}$ collisions at the ${\rm Y}(4S)$ resonance

The BABAR Collaboration

We report on measurements of the decays of $\overline{B}$ mesons into the semileptonic final states $\overline{B}\to D^{(\ast )}{\pi }^{+}{\pi }^{-}{\ell }^{-}\overline{\nu }$, where $D^{(\ast )}$ represents a…