Measurement of B→Ds(*)+D*(*) branching fractions

This article describes improved measurements by CLEO of the $B^0\to D_s^{+}{D}^{*-}$ and $B^0\to D_s^{*+}{D}^{*-}$ branching fractions, and first evidence for the decay $B^{+}\to D_s^{\left(*\right)+}{D}^{**0},$ where $D^{**0}$ represents the sum of the $D_1{\mathrm{}\left(2420\right)\mathrm{}}^0,$ $D_2^{*}{\mathrm{}\left(2460\right)\mathrm{}}^0,$ and $D_1{\mathrm{}(j=1/2\mathrm{})\mathrm{}}^{0}L=1\mathrm{}$ charm meson states. Also reported is the first measurement of the $D_s^{*+}$ polarization in the decay $B^0\to D_s^{*+}{D}^{*-}.$ A partial reconstruction technique, employing only the fully reconstructed $D_s^{+}$ and slow pion ${\pi }_s^{-}$ from the $D^{*-}\to D^0{\pi }_s^{-}$ decay, enhances sensitivity. The observed branching fractions are $\mathcal{B}{(B}^0\to D_s^{+}{D}^{*-})=(1.10\mathrm{}\pm 0.18\pm 0.10\pm 0.28)\%,$ $\mathcal{B}{(B}^0\to D_s^{*+}{D}^{*-})=(1.82\mathrm{}\pm 0.37\pm 0.24\pm 0.46)\%$, and $\mathcal{B}{(B}^{+}\to D_s^{\left(*\right)+}{D}^{**0})=(2.73\mathrm{}\pm 0.78\pm 0.48\pm 0.68)\%,$ where the first error is statistical, the second systematic, and the third is the uncertainty in the $D_s^{+}\to \phi {\pi }^{+}$ branching fraction. The measured $D_s^{*+}$ longitudinal polarization, ${\Gamma }_L/\Gamma =(50.6\mathrm{}\pm 13.9\pm 3.6)\%,$ is consistent with the factorization prediction of 54%.