Measurement of the B0 meson lifetime with partial reconstruction of B0 --> D*- pi+ and B0 --> D*- rho+ decays

The neutral $B$ meson lifetime is measured with the data collected by the BaBar detector at the PEP-II storage ring during the years 1999 and 2000, with a total integrated luminosity of 20.7 ${\rm fb}^{-1}$. The decays $B^0 \to D^{*-} \pi^+$ and $B^0 \to D^{*-} \rho^+$ are selected with a partial-reconstruction technique, yielding samples of $6970 \pm 240$ and $5520 \pm 250$ signal events, respectively. With these events, the $B^0 $ lifetime is measured to be $ 1.533 \pm 0.034 {\rm (stat.)} \pm 0.038 {\rm (syst.)} {\rm ps}$. This measurement serves as a test and validation of procedures required to measure the CP violation parameter $\sin(2\beta + \gamma)$ with partial reconstruction of these modes.