Impact on $L$-observables of a new combined analysis of $B_{d,s}\to K^{(\ast )}$ form factors

We explore the impact of a combined analysis of $B_{d,s}\to K^{(\ast )}$ form factors on a set of $L$-observables. The $L$-observables are constructed from ratios of branching fractions in $B_s\to VV,PP,PV$ versus $B_d\to VV,PP,PV$ decays with $P=K^0,{\bar{K}}^0$ and $V=K^{\ast 0},{\bar{K}}^{\ast 0}$, thereby partially reducing their hadronic uncertainties. We show the change of the Standard Model predictions of the $L$-observables under different determinations of the ratio of the relevant form factors (with correlations) including lattice QCD data and a novel light-cone sum rule analysis. In addition, we provide precise results for all $B_{d,s}\to K^{(\ast )}$ form factors in machine-readable files. We find that the inclusion of our up-to-date results, as well as the use or omission of lattice QCD data for the form factors, has a significant impact on the $L$-observables. We also discuss how the New Physics interpretation is affected by the updated form factors and present revised predictions for the mechanism identified in our analysis of $B\to VP$ decays, now employing more suitable new experimental observables defined in this paper.