Measurement of the time-dependent CP asymmetries in B {s/0} → J/ ψK {S/0}

Abstract

The first measurement of decay-time-dependent CP asymmetries in the decay B0 s → J/ψ K0 S and an updated measurement of the ratio of branching fractions B(B0 s → J/ψ K0 S )/B(B0→ J/ψ K0 S ) are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb−1 of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The results on the CP asymmetries are A∆Γ B 0 s → J/ψ K0 S = 0.49 ± 0.77 0.65 (stat) ± 0.06 (syst) , Cdir B 0 s → J/ψ K0 S = −0.28 ± 0.41 (stat) ± 0.08 (syst) , Smix B 0 s → J/ψ K0 S = −0.08 ± 0.40 (stat) ± 0.08 (syst) . The ratio B(B0 s → J/ψ K0 S )/B(B0→ J/ψ K0 S ) is measured to be 0.0431 ± 0.0017 (stat) ± 0.0012 (syst) ± 0.0025 (fs/fd) , where the last uncertainty is due to the knowledge of the B0 s and B0 production fractio