Speaker
Description
Tantalizing anomalies have been observed in tests of lepton flavour universality (LFU) that show significant deviations from the SM prediction. While the most straightforward solutions to these anomalies rely on heavy new physics impacting the vector semi-leptonic effective operators, it is also possible to consider the effects of light particles produced on-shell in the B decays. This is motivated, in particular, by the anomaly in the low-energy bin of RK* that is typically difficult to understand with only heavy mediators.
Among the possible BSM particles, ALPs are one of the most compelling candidates. Due to its shift-symmetry, the ALP contribution to the LFU ratios is suppressed by the fermion masses. Still, interesting solutions have been found in the literature, assuming lepton flavour universal scenarios, that comply with strong bounds from other observables. I will discuss departures from this assumption, as well as the plausibility of flavour assumptions behind the new regions of parameter space that will open.
