Observation of Bs0 → J/ψ K*(892)0 and Bs0 → J/ψ KS0 decays

The authors report the first observation of two Cabibbo-suppressed decay modes of the Bs0 meson. Using a sample of p(bar p) collisions at √s = 1.96 TeV corresponding to 5.9 fb-1 of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron, they search for new Bs0 decay modes in a sample of events containing J/ψ → μ+μ- decays. They reconstruct a Bs0 → J/ψ K*(892)0 signal with K*(892)0 → K+π-, observing a yield of 151 ± 25 events with a statistical significance of 8.0σ. They also reconstruct a Bs0 → J/ψ KS0 signal with KS0 → π+π-, observing a yield of 64 ± 14 events with a statistical significance of 7.2σ. From these yields, they extract the branching ratios Β(Bs0 → J/ψ K*(892)0) = (8.3 ± 3.8) x 10-5 and Β(Bs0 → J/ψ K0) = (3.5 ± 0.8) x 10-5, where statistical, systematic, and fragmentation-fraction uncertainties are included in the combined uncertainty.