Precision Measurement of CP Violation in B[0 over s] → J/ΨK[superscript +]K[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, corresponding to an integrated luminosity of 3.0 fb[superscript -1], collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96 000 B[0 over s] → J/ψK[superscript +]K[superscript -] decays, the CP-violating phase ϕ[subscript s] is measured, as well as 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. The values obtained are ϕ[subscript s] = -0.058 ± 0.049 ± 0.006 rad, Γ[subscript s] ≡ (Γ[subscript L] + Γ[subscript H])/2 = 0.6603 ± 0.0027 ± 0.0015 ps[superscript -1], and ΔΓ[subscript s] ≡ Γ[subscript L] - Γ[subscript H] = 0.0805 ± 0.0091 ± 0.0032 ps[superscript -1], where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with B[0 over s] → J/ψπ[superscript +]π[superscript -] decays gives ϕ[subscript s] = -0.010 ± 0.039 rad. All measurements are in agreement with the standard model predictions. For the first time, the phase ϕ[subscript s] is measured independently for each polarization state of the K[superscript +]K[superscript -] system and shows no evidence for polarization dependence.