Semileptonic B → D^* decays from light to τ leptons: the extraction of the form factor F₂ from data

This is the authors' abstract. We don't add key points for this paper.

We extend the Standard Model (SM) analysis of Martinelli et al. (Phys Rev D Ser 111:013005, 2025. https://doi.org/10.1103/PhysRevD.111.013005 ), which was limited to light leptons in the final state, to the semileptonic B → D^* τ ν _τ B → D ∗ τ ν τ decay. By using quantities that can be analised without the knowledge of Vcb | V cb | , we derive important information about the helicity amplitudes and the hadronic form factors that can be compared with the predictions of lattice QCD calculations. In particular, there is a difficulty in reproducing simultaneously the experimental values of R(D^*) R ( D ∗ ) and of other quantities relevant for the semitauonic decays within the SM. As a byproduct of our analysis, we also present a determination of Vcb | V cb | from the total decay rate.