Revisit to the $b\to c\tau\nu$ transition: in and beyond the SM.

We perform an analysis of the $b\to c\tau\nu$ data, including $R(D^{(*)})$, $R(J/\psi)$, $P_\tau(D^{*})$ and $F_L^{D^*}$, within and beyond the Standard Model (SM). We fit the $B\to D^{(*)}$ hadronic form factors in the HQET parametrization to the lattice and the light-cone sum rule (LCSR) results, applying the unitarity bounds derived in the analysis. We then investigate the model-independent and the leptoquark model explanations of the $b\to c\tau\nu$ anomalies. Specifically, we consider the one-operator, the two-operator new physics (NP) scenarios and the NP models with a single leptoquark which can address the $b\to c\tau\nu$ anomalies. We also give predictions for various observables including $R(D^{(*)})$ in the SM and the NP scenarios/leptoquark models based on the present form factor study and the analysis of NP.