Measurement of the weak mixing phase $\phi_s$ through time-dependent CP violation in $B^0_s \rightarrow J/\psi \phi$ decay in ATLAS

In the Standard Model of particle physics, CP violation arises due to a single complex phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. Testing the validity of the CKM mechanism as a source of CP violation is one of the major experimental challenges in particle physics today. Precise measurement of the CKM parameters therefore constrains the Standard Model, and may reveal effects beyond it. Measurement of the time-dependent decay rates of B 0 s → J/ψφ provides a theoretically clean method for extracting the CP-violating weak mixing phase φs . The Standard Model predicts φs to be very small and it is very well constrained, while in many new physics models large φs values are expected. Small deviations in a measurement of φs would be hints for the existence of the new particles. The most recent results on the CP-violating mixing phase φs and several other parameters describing the B 0 s meson system are presented from ATLAS, using √ s = 13 TeV proton-proton collision data from the LHC, are presented.