Precision Measurement of $D_s^{\ast +}$-$D_s^{+}$ Mass Difference

We measure the mass difference between $D_s^{\ast +}$ and $D_s^{+}$, $\mathrm{\Delta }{m}_s$, using the decay chain $D_s^{\ast +}\to D_s^{+}(\to K^{+}{K}^{-}{\pi }^{+}){\pi }^0$, utilizing $e^{+}{e}^{-}$ annihilation data corresponding to an integrated luminosity of 3.19 fb${}^{-1}$ collected at a center-of-mass energy of 4.178 GeV with the BESIII detector. The measured value of $\mathrm{\Delta }{m}_s=[144201.9\pm 44.2(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.})\pm 29.9(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.})\pm 15.0(\mathrm{P}\mathrm{D}\mathrm{G})]$ keV/$c^2$ is about seven times more precise than the current Particle Data Group average, where the last uncertainty is from the Particle Data Group average of the $D^{\ast +}-D^{+}$ mass difference.