Measurement of the Flavour-Specific CP-Violating Asymmetry a_sl^s in B0s Decays

The CP-violating asymmetry a_sl^s is studied using semileptonic decays of B0s and anti-B0s mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0 fb^−1. The reconstructed final states are Ds± μ∓, with the Ds± particle decaying in the ϕ π± mode. The Ds± μ∓ yields are summed over anti-B0s and B0s initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain a_sl^s = (−0.06 ± 0.50 ± 0.36)%, where the first uncertainty is statistical and the second systematic.