A measurement of ∆Γs

A bstract Using a dataset corresponding to 9 fb − 1 of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the decay modes Bₛ⁰→ J/ψ η B s 0 → J / ψη ′ and Bₛ⁰→ J/ψ π⁺π⁻ B s 0 → J / ψ π + π − are studied. The decay-width difference between the light and heavy mass eigenstates of the Bₛ⁰ B s 0 meson is measured to be ∆Γ s = 0 . 087 ± 0 . 012 ± 0 . 009 ps − 1 , where the first uncertainty is statistical and the second systematic.