Speaker
Description
The LHCb collaboration has recently set a first limit on the radiative leptonic decay of the $B_s$-meson in the region of high momentum transfer, namely $\mathcal{B} (B_s^0 \to \mu^+ \mu^- \gamma) [q^2 > (4.9 \, \rm {GeV})^2] < 2.0 \times 10^{-9}$. From the theoretical point of view, several computations of the hadronic Form Factors (FFs) entering in this decay are available in the context of quark models and Light Cone Sum Rules methods -- with results not always consistent with each other. In this talk, we will present a novel phenomenological approach to the determination of the behaviour of the hadronic FFs in $B_s \to \gamma$ decay, starting from the available LQCD data for $D_s \to \gamma$ decays. The Vector Meson Dominance approximation will be critically investigated in the $D_s$-sector and our findings will be then extended to the $B_s$-sector. We will finally use our results to develop a comparison with other determinations of the hadronic FFs and to obtain new SM predictions of the branching ratio and of other observables of interest.
