Branching Fractions

This article describes improved measurements by CLEO of the B0 → D+ s D ∗− and B0 → D∗+ s D ∗− branching fractions, and first evidence for the decay B+ → D (∗)+ s D̄∗∗0, where D̄∗∗0 represents the sum of the D̄1(2420) 0, D̄ 2(2460) 0, and D̄1(j = 1/2) 0 L = 1 charm meson states. Also reported is the first measurement of theD∗+ s polarization in the decay B 0 → D∗+ s D . A partial reconstruction technique, employing only the fully reconstructed D+ s and slow pion π s from theD ∗− → D̄0π− s decay, enhances sensitivity. The observed branching fractions are B(B0 → D+ s D ) = (1.10 ± 0.18 ± 0.10 ± 0.28)% , B(B0 → D∗+ s D ) = (1.82±0.37±0.24±0.46)% , and B(B+ → D (∗)+ s D̄∗∗0) = (2.73±0.78±0.48±0.68)%, where the first error is statistical, the second systematic, and the third is the uncertainty in theD+ s → φπ + branching fraction. The measured D∗+ s longitudinal polarization, ΓL/Γ = (50.6± 13.9± 3.6)%, is consistent with the factorization prediction of 54%. Typeset using REVTEX 4