Measurement of the CP-violating phase ø_sand the B^omeson decay width difference with B^o_s→ J/ ψø decays in ATLAS

A measurement of the B ⁰ _s decay parameters in the B ⁰ _s  → J/ψϕ channel using an integrated luminosity of 14.3 fb⁻¹ collected by the ATLAS detector from 8 TeV pp collisions at the LHC is presented. The measured parameters include the CP -violating phase ϕ _s , the decay width Γ _s and the width difference between the mass eigenstates ΔΓ _s . The values measured for the physical parameters are statistically combined with those from 4.9 fb⁻¹ of 7 TeV data, leading to the following:

In the analysis the parameter ΔΓ _s is constrained to be positive. Results for ϕ _s and ΔΓ _s are also presented as 68% and 95% likelihood contours in the ϕ _s -ΔΓ _s plane. Also measured in this decay channel are the transversity amplitudes and corresponding strong phases. All measurements are in agreement with the Standard Model predictions.