Precision measurement of the B0s–B̄⁰ₛ oscillation frequency with the decay B0s→ D−sπ+

A key ingredient to searches for physics beyond the Standard Model in B 0 s mixing phenomena is the measurement of the B 0 s – oscillation frequency, which is equivalent to the mass difference Δ m s of the B 0 s mass eigenstates. Using the world's largest B 0 s meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb −1 , collected by the LHCb experiment at the CERN LHC in 2011, a measurement of Δ m s is presented. A total of about 34 000 B 0 s → D − s π + signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be Δ m s = 17.768 ± 0.023 (stat) ± 0.006 (syst) ps −1 , which is the most precise measurement to date.