Observation of Ds+ K- and evidence for Ds+ pi- final states in neutral B decays

TL;DR

This paper reports the first observation of the B0bar -> Ds+ K- decay and evidence for B0 -> Ds+ pi- decay, providing new insights into B meson decay processes and CKM matrix elements.

Contribution

It presents the first observation of a non-spectator B meson decay and evidence for another, with measured branching fractions, expanding understanding of B decay channels.

Findings

First observation of B0bar -> Ds+ K- decay.

Evidence for B0 -> Ds+ pi- decay.

Branching fractions measured for both decays.

Abstract

We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B0bar -> Ds+ K- is found in a sample of 85 timse 10^6 B Bbar events, collected with the Belle detector at KEKB, with a branching fraction Br(B0bar -> Ds+ K-)=(4.6^{+1.2}_{-1.1} +- 1.3) times 10^{-5}. We also obtain evidence for the B0 -> Ds+ pi- decay with branching fraction Br(B0 -> Ds+ pi-)=(2.4^{+1.0}_{-0.8} +- 0.7) times 10^{-5}. This value may be used to extract a model-dependent value of |Vub|.