B → K ∗ ℓ + ℓ − decays at large recoil in the Standard Model: a theoretical reappraisal

We critically reassess the theoretical uncertainties in the standard model calculation of the b → k ∗ ℓ + ℓ − observables, focusing on the low q 2 region. we point out that even optimized observables are affected by sizable uncertainties, since hadronic contributions generated by current-current operators with charm are difficult to estimate, especially for q 2 ∼ 4m 2  ≃ 6.8 gev2. we perform a detailed numerical analysis and present both predictions and results from the fit obtained using most recent data. we find that non-factorizable power corrections of the expected order of magnitude are sufficient to give a good description of current experimental data within the standard model. we discuss in detail the q 2 dependence of the corrections and their possible interpretation as shifts of the standard model wilson coefficients.