Search for Bs0→hh decays at the Υ(5S) resonance

We have searched for Bs0→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 Υ(5S) resonance at the KEKB asymmetric-energy e+e- collider, containing 1.25x106 Bs(*)Bs(*) events. We observe the decay Bs0→K+K- and measure its branching fraction, B(Bs0→K+K-)=[3.8-0.9+1.0(stat)±0.5(syst)±0.5(fs)]x10-5. The first error is statistical, the second is systematic, and the third error is due to the uncertainty in the Bs0 production fraction in e+e-→bb events. No significant signals are seen in other decay modes, and we set upper limits at the 90% confidence level: B(Bs0→K-π+)<1.2x10-5, B(Bs0→π+π-)<2.6x10-5, and B(Bs0→K0K0)<6.6x10-5.