Phys. Rev. D 87, 031101(R) (2013) - Precise measurement of the branching fractions for ${B}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{\mathbf{(}*\mathbf{)}\mathbf{+}}{D}_{s}^{\mathbf{(}*\mathbf{)}\mathbf{\ensuremath{-}}}$ and first measurement of the ${D}_{s}^{*\mathbf{+}}{D}_{s}^{*\mathbf{\ensuremath{-}}}$ polarization using ${e}^{\mathbf{+}}{e}^{\mathbf{\ensuremath{-}}}$ collisions

Rapid Communication

Precise measurement of the branching fractions for $B_{s}^{0} \to D_{s}^{() +} D_{s}^{() -}$ and first measurement of the $D_{s}^{* +} D_{s}^{* -}$ polarization using $e^{+} e^{-}$ collisions

S. Esen et al. (Belle Collaboration)

Phys. Rev. D 87, 031101(R) – Published 12 February 2013

Abstract

We have made a precise measurement of the absolute branching fractions of $B_{s}^{0} \to D_{s}^{(*) +} D_{s}^{(*) -}$ decays using $121.4 {fb}^{- 1}$ of data recorded by the Belle experiment running at the $Υ (5 S)$ resonance. The results are $B (B_{s}^{0} \to D_{s}^{+} D_{s}^{-}) = ({0.58}_{- 0.09}^{+ 0.11} \pm 0.13) %$ , $B (B_{s}^{0} \to D_{s}^{* \pm} D_{s}^{\mp}) = ({1.76}_{- 0.22}^{+ 0.23} \pm 0.40) %$ , and $B (B_{s}^{0} \to D_{s}^{* +} D_{s}^{* -}) = ({1.98}_{- 0.31 - 0.50}^{+ 0.33 + 0.52}) %$ ; the sum is $B (B_{s}^{0} \to D_{s}^{(*) +} D_{s}^{(*) -}) = ({4.32}_{- 0.39 - 1.03}^{+ 0.42 + 1.04}) %$ . Assuming $B_{s}^{0} \to D_{s}^{(*) +} D_{s}^{(*) -}$ saturates decays to $C P$ -even final states, the branching fraction constrains the ratio $Δ Γ_{s} / \cos ϕ_{12}$ , where $Δ Γ_{s}$ is the difference in widths between the two $B_{s} − {\bar{B}}_{s}$ mass eigenstates, and $ϕ_{12}$ is the $C P$ -violating phase in $B_{s} − {\bar{B}}_{s}$ mixing. We also measure for the first time the longitudinal polarization fraction of $B_{s}^{0} \to D_{s}^{* +} D_{s}^{* -}$ ; the result is ${0.06}_{- 0.17}^{+ 0.18} \pm 0.03$ .