Mixing and CP violation in the Bs system with ATLAS

A measurement of the Bs0 → J/ψφ decay parameters, updated to include flavour tagging is reported using 4.9 fb−1 of integrated luminosity collected by the ATLAS detector from √s = 7 TeV pp collisions recorded in 2011 at the LHC. The values measured for the physical parameters are: φs = 0.12 ± 0.25 (stat.) ± 0.05 (syst.) rad ∆Γs = 0.053 ± 0.021 (stat.) ± 0.010 (syst.) ps−1 where the parameter ∆Γs is constrained to be positive. The S-wave contribution was measured and found to be compatible with zero. Results for φs and ∆Γs are in agreement with the Standard Model expectations.