Measurement of CP asymmetry in B 0 s → D ∓ s K ± decays

Abstract

We report on measurements of the time-dependent CP violating observables in B 0 s → D ∓ s K ± decays using a dataset corresponding to 1.0 fb−1 of pp collisions recorded with the LHCb detector. We find the CP violating observables C f = 0.53±0.25±0.04, A ΔΓ f = 0.37 ± 0.42 ± 0.20, AΔΓf¯¯¯=0.20±0.41±0.20, S f = −1.09±0.33±0.08, Sf¯¯¯=−0.36±0.34±0.08, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the B 0 s mixing phase −2β s leads to the first extraction of the CKM angle γ from B 0 s → D ∓ s K ± decays, finding γ = (115 + 28− 43 )° modulo 180° at 68% CL, where the error contains both statistical and systematic uncertainties.