Large off-shell effects in the ${\bar{D}}^{\ast }$ contribution to $B\to \bar{D}\pi \pi$ and $B\to \bar{D}\pi \bar{\ell }{\nu }_{\ell }$ decays.}}

A. Le-Yaouanc, J. -P. Leroy, P. Roudeau

We stress that, although the $D^{\ast }$ is very narrow (one hundred of keV), the difference between the full $D^{\ast }$ contribution to $B\to \bar{D}\pi \pi$ and its zero width limit, which ste…