Branching ratios and form factors in $B^0_s \to D^{(*)-}_s\mu^+\nu_\nu$ decays

As a necessary step towards the test of lepton flavor universality provided by the observable $R$($D$$_{s}^{(*)}$ = $B$($B$$_{s}^{0}$ → $D$$_{s}^{(*)}$$^{-}$ $\tau$$^{+}$$\nu$$_{\tau}$)/$B$($B$$_{s}^{0}$ → $D$$_{s}^{(*)}$$^{-}$ $\mu$$^{+}$$\nu$$_{\mu}$), the exlusive branching ratios and form factor of its denominator are going to be measured for the first time at an hadron collider.