Measurement of the Decay B_s^0 -> D_s^- pi^+ and Evidence for B_s^0 -> D_s^{+/-} K^{-/+} in e+e- Annihilation at sqrt(s)~10.87 GeV

TL;DR

This study measures branching fractions and masses of Bs0 decays using data from the Belle detector at the Upsilon(5S) resonance, providing new insights into Bs0 decay properties and event composition.

Contribution

First measurement of the branching fraction for Bs0 -> Ds- pi+ and evidence for Bs0 -> Ds^{+/-} K^{-/+} decays at the Upsilon(5S) energy.

Findings

Measured BR(Bs0 -> Ds- pi+) = (3.67 +0.35 -0.33 (stat.) +0.43 -0.42 (syst.) ±0.49 (f_s)) x 10^{-3}

Determined the masses M(Bs0) and M(Bs*) with high precision

Observed Bs0 -> Ds^{+/-} K^{-/+} decays with 3.5 sigma significance

Abstract

We have studied Bs0 -> Ds- pi+ and Bs0 -> Ds^(-/+) K^(+/-) decays using 23.6 /fb of data collected at the Upsilon(5S) resonance with the Belle detector at the KEKB e+e- collider. This highly pure Bs0 -> Ds- pi+ sample is used to measure the branching fraction, BR(Bs0 -> Ds- pi+)=[3.67 +0.35,-0.33}(stat.) +0.43,-0.42(syst.) +-0.49(f_s)] x 10^{-3} (f_s=N(Bs(*) Bs(*)bar)/N(b\bar b)) and the fractions of Bs0 event types at the Upsilon(5S) energy, {in particular N(Bs* Bs*bar}/N(N(Bs(*) Bs(*)bar)=(90.1 +3.8,-4.0 +-0.2)%. We also determine the masses M(Bs0)=(5364.4 +-1.3 +-0.7) MeV/c^2 and M(Bs*)=(5416.4 +-0.4 +-0.5) MeV/c^2. In addition, we observe Bs0 -> Ds^(-/+) K^(+/-) decays with a significance of 3.5\sigma and measure BR(Bs0 -> Ds^(-/+) K^(+/-))=[2.4 +1.2,-1.0(stat.) +-0.3(syst.) +-0.3(f_s)] x 10^{-4}.