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Using a dataset of 6.32 fb$^{-1}$ of $e^+ e^-$ annihilation data collectedwith the BESIII detector at center-of-mass energies between 4178 and 4226 MeV,we have measured the absolute branching fraction of the leptonic decay $D_s^+\to \tau^+ \nu_{\tau}$ via $\tau^+ \to e^+ \nu_e \bar{\nu}_{\tau}$, and find$\mathcal{B}_{D_s^+ \to \tau^+ \nu_{\tau}}=(5.27\pm0.10\pm0.12)\times10^{-2}$,where the first uncertainty is statistical and the second is systematic. Theprecision is improved by a factor of 2 compared to the previous bestmeasurement. Combining with $f_{D_s^+}$ from Lattice quantum chromodynamicscalculations or the $|V_{cs}|$ from the CKMfitter group, we extract$|V_{cs}|=0.978\pm0.009\pm0.012$ and $f_{D_s^+}= (251.1\pm2.4\pm3.0)$ MeV,respectively. Combining our result with the world averages of$\mathcal{B}_{D_s^+ \to \tau^+ \nu_{\tau}}$ and $\mathcal{B}_{D_s^+ \to \mu^+\nu_{\mu}}$, we obtain the ratio of the branching fractions $\mathcal{B}_{D_s^+\to \tau^+ \nu_{\tau}} / \mathcal{B}_{D_s^+ \to \mu^+ \nu_{\mu}} =9.72\pm0.37$, which is consistent with the standard model prediction of leptonflavor universality.

Measurement of the Absolute Branching Fraction of $D_s^+ \to \tau^+ \nu_{\tau}$ via $\tau^+ \to e^+ \nu_e \bar{\nu}_{\tau}$