Global fit to $b to c tau u$ transitions

We perform a general model-independent analysis of $b to c tau bar{ u}_tau $ transitions, including measurements of $mathcal{R}_D$, $mathcal{R}_{D^*}$, their $q^2$ differential distributions, the recently measured longitudinal $D^*$ polarization $F_L^{D^*}$, and constraints from the $B_c to tau bar{ u}_tau$ lifetime, each of which has significant impact on the fit. A global fit to a general set of Wilson coefficients of an effective low-energy Hamiltonian is presented, the solutions of which are interpreted in terms of hypothetical new-physics mediators. From the obtained results we predict selected $b to ctaubar u_tau$ observables, such as the baryonic transition $Lambda_b to Lambda_c tau bar{ u}_tau$, the ratio $mathcal{R}_{J/psi}$, the forward-backward asymmetries ${cal A}_text{FB}^{D^{(*)}}$, the $tau$ polarization asymmetries $mathcal{P}_tau^{D^{(*)}}$, and the longitudinal $D^*$ polarization fraction $F_L^{D^*}$. The latter shows presently a slight tension with any new-physics model, such that an improved measurement could have an important impact. We also discuss the potential change due the very recently announced preliminary $mathcal{R}_{D^{(*)}}$ measurement by the Belle collaboration.