- m_c}{m_{B_c} - m_{J/\Psi}}\,A_1(q^2)\,,\nonumber \\
&&T_3(q^2) = -\frac{m_b -m_c}{q^2}\Big[m_{B_c}\Big(A_1(q^2) - A_2(q^2)\Big)+m_{J/\Psi}\Big(A_2(q^2) + A_1(q^2)-2\,A_0(q^2)\Big)\Big]\,.\end{aligned}$$ A preliminary lattice calculation of $B_c \to J/\Psi$ transition form factors is reported in Ref. [@Lytle:2016ixw; @Colquhoun:2016osw].

The $B \to D$ transition form factors $F_0(q^2)$ and $F_{+}(q^2)$, calculated using lattice QCD techniques, are collected from Ref. [@Lattice:2015rga]. For the tensor form factor $F_T(q^2)$, we use Ref. [@Melikhov:2000yu]. That is $$\begin{aligned}
&&F_T(q^2)= \frac{0.69}{\Big(1-\frac{q^2}{6.4^2}\Big)\Big(1-0.56\frac{q^2}{6.4^2}\Big)}\end{aligned}$$ Similarly, for $B \to D^{\ast}$ form factors, we follow the heavy quark effective theory (HQET) approach of Ref. [@Caprini:1997mu]. We refer to Ref. [@Caprini:1997mu] for all the relevant equations.

We first perform a $\chi^2$ test to measure the disagreement of SM with the data. The $\chi^2$ is defined as $$\begin{aligned}
\chi^2 = \sum_{i}\,\frac{\Big(\mathcal O_i^{\rm th} - \mathcal O_i^{\rm exp}\Big)^2}{\Big(\Delta\,\mathcal O_i^{\rm exp}\Big)^2}\,,\end{aligned}$$ where $\mathcal O_i^{\rm exp}$ represents the measured central value of the observables and $\Delta\,\mathcal O_i^{\rm exp}$ represents corresponding $1\sigma$ uncertainty. Similarly, $\mathcal O_i^{\rm th}$ represents the theoretical prediction of the observables. We include a total of three measurements for the evaluation of $\chi^2$, namely, $R_D$, $R_{D^{\ast}}$, and $R_{J/\Psi}$. We have not included $P_{\tau}^{D^{\ast}}$ in our fit as the error associated with it is rather large. We have found $\chi^2_{\rm min} = 16.3$ in the 