Tests of Lepton Universality Using B 0 → K 0 S ℓ + ℓ − and B + → K + ℓ + ℓ − Decays

Tests of lepton universality in B 0 → K 0 S ℓ + ℓ − and B + → K* + ℓ + ℓ − decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B 0 → K 0 S e + e − and B + → K* + e + e − decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb −1 . The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B 0 → K 0 S e + e − and B + → K* + e + e − decays is reported.