Measuring the breaking of lepton flavor universality in $B\to K^*\ell^+\ell^-$

We propose measurements of weighted differences of the angular observables in the rare decays B -> K*l(+)l(-). The proposed observables are very sensitive to the difference between theWilson coefficients C-(9)(e) and C-(9)(mu) for decays into electrons and muons, respectively. At the same time, the charm-induced hadronic contributions are kinematically suppressed to less than or similar to 7% (4%) in the region 1 GeV2 <= q(2) <= 6 GeV2, as long as lepton-flavor universality breaking occurs only in C-(9)(l). This suppression becomes stronger for the region of low hadronic recoil, q(2) >= 15 GeV2.