First measurement of the CP-violating phase in B0s→J/ψ( → e+e−)ϕ decays

Abstract

A flavour-tagged time-dependent angular analysis of B0s→J/ψϕ decays is presented where the J/ψ meson is reconstructed through its decay to an e+e− pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8\,Te V, corresponding to an integrated luminosity of 3\,fb−1. The CP-violating phase and lifetime parameters of the B0s system are measured to be ϕs=0.00±0.28±0.07\,rad, ΔΓs=0.115±0.045±0.011\,ps−1 and Γs=0.608±0.018±0.012\,ps−1 where the first uncertainty is statistical and the second systematic. This is the first time that CP-violating parameters are measured in the B0s→J/ψϕ decay with an e+e− pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.