Precision Measurement of the Branching Fraction of $D^{+}\to
\mu^{+}\nu_{\mu}$
Precision Measurement of the Branching Fraction of $D^{+}\to
\mu^{+}\nu_{\mu}$
Using $20.3~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of $E_{\rm cm}=3.773$ GeV with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay $D^+\to\mu^+\nu_\mu$ to be $(3.981\pm0.079_{\rm stat}\pm0.040_{\rm syst})\times10^{-4}$. Interpreting our measurement with knowledge of the Fermi coupling constant $G_F$, …