Observation of the decay B-s(0) -> eta(c)phi and evidence for B-s(0) -> eta(c)pi(+)pi(-)

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 pp¯¯¯pp¯, 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 pp¯¯¯pp¯ decay mode, using the decay B s 0  → J/ψπ + π − as a normalisation channel. The measured branching fractions are B(B0s→ηcϕ)=(5.01±0.53±0.27±0.63)×10−4,B(B0s→ηcπ+π−)=(1.76±0.59±0.12±0.29)×10−4, B(Bs0→ηcϕ)=(5.01±0.53±0.27±0.63)×10−4,B(Bs0→ηcπ+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.