Study of semileptonic decay of ${\bar{B}}_s^0\to \varphi l^{+}{l}^{-}$ in QCD sum rule

In this work we study the semi-leptonic decay of $\bar{B}_s^0\to \phi l^+ l^-$($l=e, \mu, \tau$)withQCDsumrulemethod\mathrm{.}Wecalculatethe$\bar{B}_s^0\to \phi$ translation form factors relevant to this semi-leptonic decay, then the branching ratios of ${\bar{B}}_s^0\to \varphi l^{+}{l}^{-}$($l=e, \mu, \tau$) decays are calculated with the form factors obtained here. Our result for the branching ratio of ${\bar{B}}_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ agrees very well with the recent experimental data. For the unmeasured decay modes such as ${\bar{B}}_s^0\to \varphi e^{+}{e}^{-}$ and ${\bar{B}}_s^0\to \varphi {\tau }^{+}{\tau }^{-}$, we give theoretical predictions.