Form factor ratios for $B_s \rightarrow K \, \ell \, \nu$ and $B_s \rightarrow D_s \, \ell \, \nu$ semileptonic decays and $|V_{ub}/V_{cb}|$.

We present a lattice quantum chromodynamics determination of the ratio of the scalar and vector form factors for two semileptonic decays of the B-s meson: B-s -> Kl nu and B-s -> D(s)l nu In conjunction with future experimental data, our results for these correlated form factors will provide a new method to extract vertical bar V-ub/V-cb vertical bar which may elucidate the current tension between exclusive and inclusive determinations of these Cabibbo-Kobayashi-Maskawa mixing matrix parameters. In addition to the form factor results, we determine the ratio of the differential decay rates, and forward-backward and polarization asymmetries, for the two decays.