Observation of the leptonic decay $D^{+}\to {\tau }^{+}{\nu }_{\tau }$

BESIII Collaboration, M. Ablikim, M. N. Achasov +479

We report the first observation of $D^{+}\to {\tau }^{+}{\nu }_{\tau }$ with a significance of $5.1\sigma$. We measure ${\cal B}(D^+\toτ^+ν_τ) = (1.20\pm0.24_{\text{stat.}}\pm0.12_{\text{syst.}})\times10^{-3…