Precision measurement of the B0 s –B 0 s oscillation frequency with the decay B0 s → D − s π +

Abstract

A key ingredient to searches for physics beyond the Standard Model in B0 s mixing phenomena is the measurement of the B0 s – B 0 s oscillation frequency, which is equivalent to the mass difference 1ms of the B0 s mass eigenstates. Using the world’s largest B0 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 1ms is presented. A total of about 34 000 B0 s → D − s π + signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be 1ms = 17.768 ± 0.023 (stat) ± 0.006 (syst) ps−1 , which is the most precise measurement to date.