We report a measurement of the branching fraction of the decay $B^0\to D^{*+}{D}^{*-}$ and of the $CP$-odd component of its final state using the BABAR detector. With data corresponding to an integrated luminosity of $20.4{\text{fb}}^{-1}$ collected at the ${\rm Y}(4S)$ resonance during 1999–2000, we have reconstructed 38 candidate signal events in the mode $B^0\to D^{*+}{D}^{*-}$ with an estimated background of $6.2\pm 0.5$ events. From these events, we determine the branching fraction to be $\mathcal{B}(B^0\to D^{*+}{D}^{*-})=[8.3\pm 1.6(\text{stat})\pm 1.2(\text{syst})]\times {10}^{-4}$. The measured $CP$-odd fraction of the final state is $0.22\pm 0.18(\text{stat})\pm 0.03(\text{syst})$.

• Received 5 March 2002

DOI:https://doi.org/10.1103/PhysRevLett.89.061801