Leptonic branching ratio of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ϒ</mml:mi><mml:mn/><mml:mo>(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo>)</mml:mo><mml:mn/></mml:math>

Using the CLEO magnetic detector at the Cornell Electron Storage Ring, we find $B(\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})=0.018\ifmmode\pm\else\textpm\fi{}0.008 (\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{l}) \ifmmode\pm\else\textpm\fi{}0.005 (\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{m}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{c})$ and $B(\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}})=0.017 \ifmmode\pm\else\textpm\fi{}0.015\ifmmode\pm\else\textpm\fi{}0.006$.