Measurement of the CP-violating weak phase phi_s and the decay width difference DeltaGamma_s using the Bs to J/psi phi(1020) decay channel in pp collisions at sqrt(s) = 8 TeV

The CP-violating weak phase ϕsϕs of the View the MathML sourceBs0 meson and the decay width difference ΔΓsΔΓs of the View the MathML sourceBs0 light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of View the MathML sourceBs0→J/ψϕ(1020)→μ+μ−K+K− decays. The analysed data set corresponds to an integrated luminosity of View the MathML source19.7fb−1 collected in pp collisions at a centre-of-mass energy of View the MathML source8TeV. A total of 49 200 reconstructed View the MathML sourceBs0 decays are used to extract the values of ϕsϕs and ΔΓsΔΓs by performing a time-dependent and flavour-tagged angular analysis of the μ+μ−K+K−μ+μ−K+K− final state. The weak phase is measured to be View the MathML sourceϕs=−0.075±0.097(stat)±0.031(syst) rad, and the decay width difference is View the MathML sourceΔΓs=0.095±0.013(stat)±0.007(syst) ps−1.