Observation of B0→D ^̄0K+ ^K- and evidence for Bs0→D ^̄0K+ ^K-

The first observation of the decay B0→D ^̄0K ⁺K ^- is reported from an analysis of 0.62fb ^-1 of pp collision data collected with the LHCb detector. Its branching fraction is measured relative to that of the topologically similar decay B0→D ^̄0π ⁺π ^- to be B(B0→D ^̄0K ⁺K ^-)B(B0→D ^̄0π ⁺π ^-)=0.056±0.011±0.007,where the first uncertainty is statistical and the second is systematic. The significance of the signal is 5.8σ. Evidence, with 3.8σ significance, for Bs0→D ^̄0K ⁺K ^- decays is also presented. The relative branching fraction is measured to be B(Bs0→D ^̄0K ⁺K ^-)B(B0→D ^̄0K ⁺K ^-)=0.90±0.27±0.20. These channels are of interest to study the mechanisms behind hadronic B decays, and open new possibilities for CP violation analyses with larger data sets.