Observation of the decay B s 0 → η c ϕ and evidence for B s 0 → η c π + π -

Abstract

A study of B s 0 → η c ϕ and B s 0 → η c 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 B s 0 → η c ϕ is reported, where the η c meson is reconstructed in the p\overline{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 B s 0 → J/ ψϕ is used as a normalisation channel. Evidence is also reported for the decay B s 0 → η c π + π -, where the η c meson is reconstructed in the p\overline{p} decay mode, using the decay B s 0 → J/ ψπ + π - as a normalisation channel. The measured branching fractions are B({B}_s^0\to {η}_cφ )=(5.01± 0.53± 0.27± 0.63)× {10}^{-4}, B({B}_s^0\to {η}_c{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.