Precise measurement of the $D_s^{+}$ lifetime at Belle II

We measure the lifetime of the $D_s^{+}$ meson using a data sample of 207 fb${}^{-1}$ collected by the Belle II experiment running at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The lifetime is determined by fitting the decay-time distribution of a sample of $116\times {10}^3$ $D_s^{+}\to \phi {\pi }^{+}$ decays. Our result is ${\tau }_{D_s^{+}}^{}=(499.5\pm 1.7\pm 0.9)$ fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements.