New determination of |V<inf>ub</inf> /V<inf>cb</inf> | from Bs0 ? {K ^-, Ds- }µ ⁺ ?

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 q 2 with more precise lattice QCD results at large q 2. We obtain a consistent description of the form factors in the full q 2 range. Applying these results to a recent LHCb measurement of branching ratios for the decays Bs0 ? {K -, Ds- }µ + ?µ, we determine the ratio of Cabibbo-Kobayashi-Maskawa elements |VubVcb|q2<7GeV2=0.0681±0.0040and|VubVcb|q2>7GeV2=0.0801±0.0047, which are mutually compatible at the 1.9s level. We further comment on the sensitivity to Beyond the Standard Model effects through measurements of the shape of Bs0 ? K - µ + ?µ decays, in light of recent limits on such effects from other exclusive b ? ul? processes.