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

TL;DR

This paper reports improved measurements of specific B meson decay branching fractions, evidence for a new decay mode, and the first polarization measurement, using a partial reconstruction technique to enhance sensitivity.

Contribution

It provides the first evidence for the decay B+ to D_s^{(*)+} D^{**0} and measures the D_s^{*+} polarization, advancing understanding of B meson decay dynamics.

Findings

Branching fraction for B^0 to D_s^+ D^{*-} is (1.10 ± 0.18 ± 0.10 ± 0.28)%

Branching fraction for B^0 to D_s^{*+} D^{*-} is (1.82 ± 0.37 ± 0.24 ± 0.46)%

First measurement of D_s^{*+} polarization in B^0 to D_s^{*+} D^{*-} decay

Abstract

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 $B^+ \to D_s^{(*)+} \bar{D}^{**0}$, where $\bar{D}^{**0}$ represents the sum of the $\bar{D}_1(2420)^0$, $\bar{D}_2^*(2460)^0$, and $\bar{D}_1(j=1/2)^0$ L=1 charm meson states. Also reported is the first measurement of the $D_s^{*+}$ 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 $D^{*-} \to \bar{D}^0 \pi^-_s$ decay, enhances sensitivity. The observed branching fractions are ${\mathcal B} (B^0 \to D_s^+ D^{*-}) = (1.10 \pm 0.18 \pm 0.10 \pm 0.28)%$, ${\mathcal B} (B^0 \to D_s^{*+} D^{*-}) = (1.82 \pm 0.37 \pm 0.24 \pm 0.46)%$, and ${\mathcal B} (B^+ \to D_s^{(*)+} \bar{D}^{**0}) = (2.73 \pm 0.78 \pm 0.48 \pm 0.68)%$, where the first error is statistical, the second systematic, and the third is due to the uncertainty in the $D_s^+ \to \phi \pi^+$ branching fraction. The measured $D_s^{*+}$ longitudinal polarization, $\Gamma_L/\Gamma = (50.6 \pm 13.9 \pm 3.6)%$, is consistent with the factorization prediction of 54%.