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

Aubert, B. et al. (2009) Direct CP, Lepton Flavor, and Isospin Asymmetries in the Decays B→K(*)l+l-. Physical Review Letters, 102 (9). 091803. ISSN 0031-9007

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 384×106 BB̅ events collected with the BABAR detector at the PEP-II e+e- collider. We find no evidence for direct CP or lepton-flavor asymmetries. However, for dilepton masses below the J/ψ resonance, we find evidence for unexpectedly large isospin asymmetries in both B→Kl+l- and B→K*l+l- which differ, respectively, by 3.2σ and 2.7σ, including systematic uncertainties, from the standard model expectations.

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