  The two B^0 decay processes B^0 --> D^{*-}pi^+ and B^0 --> D^{*-}l^+nu have
been studied by means of a partial reconstruction technique using a data sample
collected with the BABAR detector at the PEP-II storage ring. To increase
statistics, only the soft pi^- from the decay D^{*-} --> pi^-D^0 was used in
association with either an oppositely-charged high-momentum pion or lepton.
Events were then identified by exploiting the constraints from the simple
kinematics of Y(4S) decays. A clear signature is obtained in each case. The
position of the B^0 decay point was obtained from the reconstructed
pi^+(l^+)pi^- vertex. The position of the other anti-B^0 in the event was also
determined. Taking advantage of the boost given to the Y(4S) system by the
asymmetric beam energies of PEP-II, the lifetime of the B^0 meson has been
measured from the separation distance between the two vertices along the beam
direction. The preliminary results are tau_B0 = 1.55+/-0.05+/-0.07 ps, tau_B0 =
1.62+/-0.02+/-0.09 ps, respectively for the B^0 --> D^{*-}pi^+ and B^0 -->
D^{*-}l^+nu channels.
