The Dispersive Matrix perspective on Lepton Flavour Universality observables

Abstract

We review the results of the application of the Dispersion Matrix method to semileptonic charged-current B → D (*) decays. This approach allows to determine the hadronic form factors in a model-independent and non-perturbative way. Starting from lattice results at large values of the momentum transfer (or, equivalently, at low recoil), we are able to describe the form factors in their whole kinematical range without introducing any assumption on the functional dependence on their momentum transfer. We will focus on fully-theoretical determinations of the R(D (*)) ratios, which are an important test of Lepton Flavour Universality. Our Dispersion Matrix analysis allows to reduce the tensions among the theoretical and the experimental determinations of these quantities.