Measurement of CP violation and the B[0 over s] meson decay width difference with B[0 over s] → J/ψK[superscript +]K[superscript −] and B[0 over s] → J/ψπ[superscript +]π[superscript −] decays

Abstract

The time-dependent CP asymmetry in B[0 over s] → J/ψK[superscript +]K[superscript −] decays is measured using pp collision data at √s = 7 TeV, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected with the LHCb detector. The decay-time distribution is characterized by the decay widths Γ[subscript L] and Γ[subscript H] of the light and heavy mass eigenstates of the B[0 over s]−[bar over B][0 over s] system and by a CP-violating phase ϕ[subscript s]. In a sample of 27 617 B[0 over s] → J/ψK[superscript +]K[superscript −] decays, where the dominant contribution comes from B[0 over s] → J/ψϕ decays, these parameters are measured to be ϕ[subscript s] = 0.07 ± 0.09(stat) ± 0.01(syst) rad, Γ[subscript s] ≡ (Γ[subscript L] + Γ[subscript H])/2 = 0.663 ± 0.005(stat) ± 0.006(syst) ps[superscript −1], and ΔΓ[subscript s] ≡ Γ[subscript L] − Γ[subscript H] = 0.100 ± 0.016(stat) ± 0.003(syst) ps[superscript −1], corresponding to the single most precise determination of ϕ[subscript s], ΔΓ[subscript s], and Γ[subscript s]. The result of performing a combined analysis with B[0 over s] →J/ψπ[superscript +]π[superscript −] decays gives ϕ[subscript s] = 0.01 ± 0.07(stat) ± 0.01(syst) rad, Γ[subscript s] = 0.661 ± 0.004(stat) ± 0.006(syst) ps[superscript −1], and ΔΓ[subscript s] = 0.106 ± 0.011(stat) ± 0.007(syst) ps[superscript −1]. All measurements are in agreement with the Standard Model predictions.