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 q2 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 q2 ∼ 4m2c  ≃ 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 q2 dependence of the corrections and their possible interpretation as shifts of the Standard Model Wilson coefficients.