New determination of |Vub/Vcb| from Bs0→ {K−, Ds−}μ+ν.

We update the full set of B ¯ s → K form factors using light-cone sum rules with an on-shell kaon. Our approach determines the relevant sum rule parameters — the duality thresholds — from a Bayesian fit for the first time. Using a modified version of the Boyd-Grinstein-Lebed parametrisation, we combine our sum rule results at low momentum transfer q2 with more precise lattice QCD results at large q2. We obtain a consistent description of the form factors in the full q2 range. Applying these results to a recent LHCb measurement of branching ratios for the decays B s 0 → {K−, D s − }μ+νμ, we determine the ratio of Cabibbo-Kobayashi-Maskawa elements V ub V cb q 2 < 7 GeV 2 = 0.0681 ± 0.0040 and V ub V cb q 2 > 7 GeV 2 = 0.0801 ± 0.0047 , which are mutually compatible at the 1.9σ level. We further comment on the sensitivity to Beyond the Standard Model effects through measurements of the shape of B s 0 → K−μ+νμ decays, in light of recent limits on such effects from other exclusive b → uℓν processes. [ABSTRACT FROM AUTHOR]