Determination of the branching fractions of B_S⁰→ D_S^∓K^∓ and B⁰ → D_S⁻K⁺

Measurements are presented of the branching fractions of the decays BS 0 → DS ∓K∓ and B0 → DS −K+ relative to the decays BS 0 → DS −π+ and B0 → D−π+, respectively. The data used correspond to an integrated luminosity of 3.0 fb−1 of proton-proton collisions. The ratios of branching fractions are
B(B0
s → D∓s K∓)B(B0s → D−s π+)= 0.0752 ± 0.0015 ± 0.0019
and
B(B0 → D−s K+)B(B0 → D−π+)= 0.0129 ± 0.0005 ± 0.0008,
where the uncertainties are statistical and systematic, respectively.