CP violation in Bs decays (ATLAS)

The measurement of decay of Bs0 mesons to the Jψφ final state is presented, based on an analysis−1 of 13 TeV proton–proton collisions using the full Run 2 dataset corresponding to 139 fb luminosity, collected with the ATLAS detector at the LHC. The following quantities are measured: the CP-violating phase φs, the width difference ∆Γs between the Bs0 meson mass eigenstates, their mass difference ∆ms, and the average decay width Γs. The transversity amplitudes and corresponding strong phases are also reported. This is the first measurement of ∆ms made by the ATLAS collaboration. The observed values are: φs = − 0.069 ± 0.030 (stat.) ± 0.020 (syst.) rad, ∆Γs =0.0620 ± 0.0034 (stat.) ± 0.0016 (syst.) ps−1, ∆ms = 17.889 ± 0.060 (stat.) ± 0.061 (syst.) ps−1, Γs = 0.6695 ± 0.0011 (stat.) ± 0.0011 (syst.) ps−1.