Evidence for the decay Bₛ⁰→ φ η

A bstract Using a dataset corresponding to an integrated luminosity of 9 fb − 1 collected in proton-proton collisions between 2011 and 2018 by the LHCb experiment, evidence is found for the decay Bₛ⁰→ φ η B s 0 → ϕη ′ with 3 . 5 σ significance. The branching ratio relative to the Bₛ⁰→ φ φ B s 0 → ϕϕ decay is determined to be ℛ = (3 . 56 ± 0 . 79 ± 0 . 18 ± 0 . 06) × 10 − 2 . This corresponds to a branching fraction, B(Bₛ⁰→ φ η^)=(0.66± 0.15± 0.03± 0.02)× 10⁻⁶ B B s 0 → ϕη ′ = 0.66 ± 0.15 ± 0.03 ± 0.02 × 10 − 6 where, in both cases, the first uncertainty is statistical, the second systematic, and the third due to external branching fractions.