Revealing hadronic effects in B-meson decays

Indirect New Physics searches are becoming increasingly important in the quest for physics beyond the Standard Model (SM). Since these heavily rely on the precision that can be obtained both in theory and in experiments, being able to achieve good control over non-perturbative effects, which are usually the main source of theoretical uncertainty, is of utmost relevance. With this postdoctoral fellowship, I will perform a comprehensive study of non-factorisable soft-gluon contributions in B-meson decays, focusing on the tree-level non-leptonic decays like $\bar B^0 \to D^+ K^-$, and on the rare semileptonic decays like $B_s \to \phi \ell^+ \ell^-$. In fact, for both types of processes, several tensions have been observed between the SM predictions and the corresponding data, and for both types of discrepancies, the dominant source of theoretical uncertainty stems from hadronic effects. Specifically, the computation will be performed using the well-established framework of light-cone sum rules (LCSR), employing the light meson (\pi,\phi, K^{(*)}) light-cone distribution amplitudes (LCDAs). The proposed project will represent the first calculation of these hadronic effects within this method and will make it possible to circumvent current challenges that arise when using B-meson LCDAs. Furthermore, particularly for the rare semileptonic decays introduced above, this approach will lead to a significant reduction of the theoretical uncertainties, as local and non-local form factors will be computed within LCSR using the same inputs. Therefore, the proposed research will be of considerable help in assessing the nature of the observed tensions and ultimately in exploiting the rich amount of future data available.