Observation of the Decay B0s → ηc ϕ and Evidence for B0s → ηc π+ π−

A study of B0s → ηc ϕ and B0s → ηc π+ π− decays is performed using pp collision data corresponding to an integrated luminosity of 3.0 fb^−1, collected with the LHCb detector in Run 1 of the LHC. The observation of the decay B0s → ηc ϕ is reported, where the ηc meson is reconstructed in the p anti-p, K+ K− π+ π−, π+ π− π+ π− and K+ K− K+ K− decay modes and the ϕ(1020) in the K+ K− decay mode. The decay B0s → J/ψ ϕ is used as a normalisation channel. Evidence is also reported for the decay B0s → ηc π+ π−, where the ηc meson is reconstructed in the p anti-p decay mode, using the decay B0s → J/ψ π+ π− as a normalisation channel. The measured branching fractions are B(B0s → ηc ϕ) = (5.01 ± 0.53 ± 0.27 ± 0.63) × 10^−4, B(B0s → ηc π+ π−) = (1.76 ± 0.59 ± 0.12 ± 0.29) × 10^−4, B(B0s → ηc ϕ) = (5.01 ± 0.53 ± 0.27 ± 0.63) × 10^−4, B(B0s → ηc π+ π−) = (1.76 ± 0.59 ± 0.12 ± 0.29) × 10^−4, where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions.