We report the first observation of the exclusive decays $\overline{B}\to D^{(*)}{K}^{*-}$, using $9.66\times {10}^6$ $B\overline{B}$ pairs collected at the $\Upsilon \left(4S\right)$ with the CLEO detector. We measure the following branching fractions: $B(B^{-}\to D^0{K}^{*-})=(6.1\pm 1.6\pm 1.7)\times {10}^{-4\mathrm{}}$, $B({\overline{B}}^0\to D^{+}{K}^{*-})=(3.7\pm 1.5\pm 1.0)\times {10}^{-4\mathrm{}}$, $B({\overline{B}}^0\to D^{*+}{K}^{*-})=(3.8\pm 1.3\pm 0.8)\times {10}^{-4\mathrm{}}$, and $B(B^{-}\to D^{*0\mathrm{}}{K}^{*-})=(7.7\pm 2.2\pm 2.6)\times {10}^{-4\mathrm{}}$. The $\overline{B}\to D^{*}{K}^{*-}$ branching ratios are the averages of those corresponding to the 00 and 11 helicity states. The errors shown are statistical and systematic, respectively.

• Received 21 December 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.101803