Charming penguins and lepton universality violation in $$\varvec{b \rightarrow s \ell ^+ \ell ^-}$$ decays

Abstract The LHCb experiment has recently presented new results on Lepton Universality Violation (LUV) in $$B \rightarrow K^{(*)} \ell ^+ ^-$$ B → K ( ∗ ) ℓ + - decays involving $$K_S$$ S the final state, which strengthen recent evidence of LUV obtained $$B^+ K^{+} and previous measurements K^{*0} 0 . While observables Standard Model are theoretically clean, their predictions New Physics scenarios sensitive to details hadronic dynamics, particular charming penguin contribution. In this work, we show how a conservative treatment uncertainties is crucial not only assess significance deviations from but also obtain picture responsible for LUV. Adopting very general parameterization penguins, find that: (i) current data hint at sizable $$q^2$$ q 2 helicity dependence charm loop amplitudes; (ii) NP solutions B anomalies favour left-handed or an axial lepton coupling rather than vector one.