A measurement of $\mathrm{\Delta }{\mathrm{\Gamma }}_s$

Using a dataset corresponding to $9{\mathrm{f}\mathrm{b}}^{-1}$ of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the decay modes $B_s^0\to J\mathrm{/}\psi {\eta }^{\mathrm{\prime }}$ and $B_s^0\to J\mathrm{/}\psi {\pi }^{+}{\pi }^{-}$ are studied. The decay-width difference between the light and heavy mass eigenstates of the $B_s^0$ meson is measured to be $\mathrm{\Delta }{\mathrm{\Gamma }}_s=0.087\pm 0.012\pm 0.009{\mathrm{p}\mathrm{s}}^{-1}$, where the first uncertainty is statistical and the second systematic.