First observation of the decay Bs --> Ds K and measurement of the ratio of branching fractions Br(Bs --> DsK)/Br(Bs --> Ds pi)

TL;DR

This paper reports the first observation of the decay Bs --> Ds K and measures its branching fraction relative to Bs --> Ds pi using data from proton-antiproton collisions at Fermilab, with a significance of 8.1 sigma.

Contribution

It provides the first observation of Bs --> Ds K decay and quantifies its branching ratio relative to Bs --> Ds pi, using a combined mass and particle ID fit.

Findings

First observation of Bs --> Ds K decay with 8.1 sigma significance.

Measured ratio of branching fractions: 0.097 +- 0.018 (stat) +- 0.009 (sys).

Utilized 1.2 fb^-1 of data from Fermilab Tevatron.

Abstract

A combined mass and particle identification fit is used to make the first observation of the decay Bs --> Ds K and measure the branching fraction of Bs --> Ds K relative to Bs --> Ds pi. This analysis uses 1.2 fb^-1 integrated luminosity of pbar-p collisions at sqrt(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron collider. We observe a Bs --> Ds K signal with a statistical significance of 8.1 sigma and measure Br(Bs --> Ds K)/Br(Bs --> Ds pi) = 0.097 +- 0.018(stat) +- 0.009(sys).