Measurement of the CP-violating weak phase φ_s and the decay width difference ΔΓ_s using the B⁰_s→J/ψφ(1020) decay channel in pp collisions at √s= 8 TeV

The CP-violating weak phase φ_s of the B⁰_s meson and the decay width difference ΔΓ_s of the B⁰_s light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of B⁰_s→J/ψφ(1020) →μ⁺μ⁻K⁺K⁻ decays. The analysed data set corresponds to an integrated luminosity of 19.7 fb⁻¹ collected in pp collisions at a centre-of-mass energy of 8 TeV. A total of 49200 reconstructed B⁰_s decays are used to extract the values of φ_s and ΔΓ_s by performing a time-dependent and flavour-tagged angular analysis of the μ⁺μ⁻K⁺K⁻ final state. The weak phase is measured to be φ_s=−0.075 ±0.097 (stat) ±0.031 (syst) rad, and the decay width difference is ΔΓ_s=0.095 ±0.013 (stat) ±0.007 (syst) ps⁻¹.