Search for B_{s}^{0}->hh Decays at the $\Upsilon(5S)$ Resonance

TL;DR

This study searches for specific B_s^0 decay modes at the  resonance, reports the first measurement of B_s^0K^+K^- decay, and sets upper limits on other decay channels using data from the Belle detector.

Contribution

First measurement of the B_s^0K^+K^- decay branching fraction at the  resonance and establishment of upper limits for other decay modes.

Findings

Observed B_s^0K^+K^- decay with measured branching fraction.

No significant signals for other decay modes.

Set upper limits on branching fractions for K^- ext{}+ ext{},  ext{+} ext{ }and K^0ar{K}^0 decays.

Abstract

We have searched for B_{s}^{0}->hh decays, where h stands for a charged or neutral kaon, or a charged pion. These results are based on a 23.6 fb^{-1} data sample collected with the Belle detector on the \Upsilon(5S) resonance at the KEKB asymmetric-energy e^{+}e^{-} collider, containing 1.25x10^6 B_{s}^{(*)}\bar{B}_{s}^{(*)} events. We observe the decay B_{s}^{0}->K^{+}K^{-} and measure its branching fraction, \mathcal{B}(B_{s}^{0}->K^{+}K^{-}) = [3.8_{-0.9}^{+1.0}(\mathrm{stat})\pm 0.5(\mathrm{syst})\pm 0.5(f_s)] \times 10^{-5}. The first error is statistical, the second is systematic, and the third error is due to the uncertainty in the B^0_s production fraction in $e^+e^-\to b\bar{b}$ events. No significant signals are seen in other decay modes, and we set upper limits at 90% confidence level: \mathcal{B}(B_{s}^{0}->K^-\pi^{+})< 2.6 \times 10^{-5}, \mathcal{B}(B_{s}^{0}->\pi^{+}\pi^{-})< 1.2 \times 10^{-5} and \mathcal{B}(B_{s}^{0}->K^0\bar{K}^0) < 6.6\times 10^{-5}.