SM. The $\chi^2_{\rm min}$ in the SM is obtained by performing a random scan of all the theory input parameters such as CKM matrix elements, meson decay constant, and meson to meson form factors within $1\sigma$ of their central values. The corresponding best estimates for all the observables are listed in Table. \[tab2\].

Let us now evaluate $\chi^2_{\rm min}$ for various NP scenarios. First we consider that NP contributions are coming from an operator characterized by a single NP Wilson Coefficient (WC). We have considered total $10$ such NP scenarios that involve left handed as well as right handed neutrino interactions. The $\chi^2_{\rm min}$ obtained in each scenario and the corresponding best estimates of all the observables are listed in Table. \[tab2\]. We observe that we obtain the best fit to the data with $\widetilde{T}_L$ NP coupling which corresponds to $\chi^2_{\rm min}=1.7$ followed by $V_L$, $\widetilde{V}_L$, and $\widetilde{V}_R$ with $\chi^2_{\rm min}= 2.1$ each. The branching ratio of $B_c \to \tau\nu$ obtained in each of these scenarios is consistent with $\mathcal B(B_c \to \tau\nu) \le 5\%$ obtained in the SM. With $\widetilde{T}_L$ NP coupling, although the the best estimates of $R_{D^{\ast}}$ and $R_{J/\Psi}$ lie inside the $1\sigma$ experimental range, the best 