Measurement of the CP-violating phase φs and the Bs⁰ meson decay width difference with Bs⁰ → J/ψφ decays in ATLAS

Abstract

A measurement of the B s 0 decay parameters in the B s 0 → 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: ϕs=−0.090±0.078(stat.)±0.041(syst.)radΔΓs=0.085±0.011(stat.)±0.007(syst.)ps−1Γs=0.675±0.003(stat.)±0.003(syst.)ps−1. 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.