Measurements of B --> D_s^{(*)+} D^{*(*)} Branching Fractions

Abstract

This article describes improved measurements by CLEO of the $B^0\to D_s^{+}{D}^{\ast -}$ and $B^0\to D_s^{\ast +}{D}^{\ast -}$ branching fractions, and first evidence for the decay $B^{+}\to D_s^{(\ast )+}{\bar{D}}^{\ast \ast 0}$, where ${\bar{D}}^{\ast \ast 0}$ represents the sum of the ${\bar{D}}_1(2420{)}^0$, ${\bar{D}}_2^{\ast }(2460{)}^0$, and ${\bar{D}}_1(j=1/2{)}^0$ L=1 charm meson states. Also reported is the first measurement of the $D_s^{\ast +}$ polarization in the decay $B^0\to D_s^{\ast +}{D}^{\ast -}$. A partial reconstruction technique, employing only the fully reconstructed $D_s^{+}$ and slow pion $\ddot{I}{€}_s^{-}$ from the $D^{\ast -}\to {\bar{D}}^0\ddot{I}{€}_s^{-}$ decay, enhances sensitivity. The observed branching fractions are $\mathcal{B}(B^0\to D_s^{+}{D}^{\ast -})=(1.10\pm 0.18\pm 0.10\pm 0.28)$, $\mathcal{B}(B^0\to D_s^{\ast +}{D}^{\ast -})=(1.82\pm 0.37\pm 0.24\pm 0.46)$, and $\mathcal{B}(B^{+}\to D_s^{(\ast )+}{\bar{D}}^{\ast \ast 0})=(2.73\pm 0.78\pm 0.48\pm 0.68)$, where the first error is statistical, the second systematic, and the third is due to the uncertainty in the $D_s^{+}\to \ddot{I}•\ddot{I}{€}^{+}$ branching fraction. The measured $D_s^{\ast +}$ longitudinal polarization, $\hat{I}{“}_L/\hat{I}“=(50.6\pm 13.9\pm 3.6)$, is consistent with the factorization prediction of 54%.

26 pages (LaTeX), 15 figures. To be submitted to PRD