Direct CP, Lepton Flavor, and Isospin Asymmetries in the Decays B→K(*)l+l−

Abstract

We measure branching fractions and integrated rate asymmetries for the rare decays B → K ( * ) l + l − , where l + l − is either e + e − or μ + μ − , using a sample of 384 × 10 6 B ¯¯¯ B events collected with the BABAR detector at the PEP-II e + e − collider. We find no evidence for direct C P or lepton-flavor asymmetries. However, for dilepton masses below the J / ψ resonance, we find evidence for unexpectedly large isospin asymmetries in both B → K l + l − and B → K ∗ l + l − which differ, respectively, by 3.2 σ and 2.7 σ , including systematic uncertainties, from the standard model expectations.