Leptonic Decay of Upsilon, a Possible Signature of New Physics

Yu-Jie Zhang, Hua-Sheng Shao

We calculate the inclusive decay width of ${\rm Y}\to l^{+}{l}^{-}$. Then we get the ratio $R_{\tau \mu }=\Gamma [{\rm Y}\to {\tau }^{+}{\tau }^{-}]/\Gamma [{\rm Y}\to {\mu }^{+}{\mu }^{-}]$ to $\mathcal{O}(\alpha )$ and $\mathcal{O}({\alpha }_s^2)$ within the Standard…