Exclusive determinations of $\vert V_{cb} \vert$ and $R(D^{*})$ through unitarity

Understand

In this work we apply the Dispersive Matrix (DM) method of Refs.

• [1,2] to the lattice computations of the Form Factors (FFs) entering the semileptonic $B \to D^* \ell \nu_\ell$ decays, recently produced by the FNAL/MILC Collaborations [3] at small, but non-vanishing values of the recoil variable ($w-1$).
• Thanks to the DM method we obtain the FFs in the whole kinematical range accessible to the decay in a completely model-independent and non-perturbative way, implementing exactly both unitarity and kinematical constraints.
• Using our theoretical bands of the FFs we extract $\vert V_{cb} \vert$ from the experimental data and compute the theoretical value of $R(D^*)$.