Phys. Rev. Lett. 103, 191802 (2009) - First Observation of ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{\ifmmode\pm\else\textpm\fi{}}{K}^{\ensuremath{\mp}}$ and Measurement of the Ratio of Branching Fractions $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{\ifmmode\pm\else\textpm\fi{}}{K}^{\ensuremath{\mp}})/\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$

First Observation of ${\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}$ and Measurement of the Ratio of Branching Fractions $B ({\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}) / B ({\bar{B}}_{s}^{0} \to D_{s}^{+} π^{-})$

T. Aaltonen et al. (CDF Collaboration)

Phys. Rev. Lett. 103, 191802 – Published 3 November 2009

Abstract

A combined mass and particle identification fit is used to make the first observation of the decay ${\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}$ and measure the branching fraction of ${\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}$ relative to ${\bar{B}}_{s}^{0} \to D_{s}^{+} π^{-}$ . This analysis uses $1.2 {fb}^{- 1}$ integrated luminosity of $p \bar{p}$ collisions at $\sqrt{s} = 1.96 TeV$ collected with the CDF II detector at the Fermilab Tevatron collider. We observe a ${\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}$ signal with a statistical significance of $8.1 σ$ and measure $B ({\bar{B}}_{s}^{0} \to D_{s}^{\pm} K^{\mp}) / B ({\bar{B}}_{s}^{0} \to D_{s}^{+} π^{-}) = 0.097 \pm 0.018 (stat) \pm 0.009 (syst)$ .