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Several measurements on $R_D, R_{D^*}$, and $R_{J/ \psi}$ by the BaBar,Belle, and LHCb experiments show significant deviations from their StandardModel (SM) predictions, which illustrate the fact that the concept of leptonflavor universality (LFU) is violated in semileptonic $B$ meson as well asleptonic $\Upsilon(ns)(n=1,2,3)$ decays. Recently BaBar experiment announcedthat at $1.8\sigma$ level, $R_\Upsilon(3s)= {\rm Br}(\Upsilon(3s) \to \tau\bar{\tau})/{\rm Br}(\Upsilon(3s) \to \mu \bar{\mu})$ shows an acceptance withthe SM. These fascinating findings point towards the possible implication ofnew physics in the $b \to c \tau \bar{\nu}$ transitions, which in turn, createsa new direction to look for new physics in $b \bar{b} \to \tau \bar{\tau} $process. Thereby, the new physics contributions to the $b \to c \tau \bar{\nu}$process would inevitably alter the $b \bar{b} \to \tau \bar{\tau} $transitions. Here we conduct a $\chi^{2}$ fit to constraining the newparameters by using the measured values of $ R_D$, $R{_D*}$, $ R_{J/ \psi}$, $R_{X_C}$, $F_L (D^*)$ and $P_{\tau} (D^*)$. In this context, we investigate theeffect of constrained new physics couplings on the branching ratios and LFUparameters $R_{\Upsilon(ns)}$ through leptoquark models such as $S_3,\tilde{S_1}, \tilde{R_2}, U_1, U_3 $ and $ V_2$.

Investigating $ \Upsilon(ns) \to \tau^+ \tau^- $ decay in the Leptoquark scenario