Determination of f<inf>s</inf>/f<inf>d</inf> for 7 TeV pp collisions and measurement of the B0→D^-K⁺ branching fraction

The relative abundance of the three decay modes B0→D ^-K ⁺, B0→D ^-π ⁺, and Bs0→Ds- π ⁺ produced in 7 TeV pp collisions at the LHC is determined from data corresponding to an integrated luminosity of 35pb ^-1. The branching fraction of B0→D ^-K ⁺ is found to be B(B0→D ^-K ⁺)=(2.01±0.18stat±0.14syst) ×10 ^-4. The ratio of fragmentation fractions f _s/f _d is determined through the relative abundance of Bs0→Ds-π ⁺ to B0→D ^-K ⁺ and B0→D ^-π ⁺, leading to f _s/f _d=0.253±0.017±0.017±0.020, where the uncertainties are statistical, systematic, and theoretical, respectively.