Direct $CP$, Lepton Flavor, and Isospin Asymmetries in the Decays $B\ensuremath{\rightarrow}{K}^{(*)}{l}^{+}{l}^{\ensuremath{-}}$

Direct $C P$ , Lepton Flavor, and Isospin Asymmetries in the Decays $B \to K^{(*)} l^{+} l^{-}$

B. Aubert et al. (BABAR Collaboration)

Phys. Rev. Lett. 102, 091803 – Published 4 March 2009

Abstract

We measure branching fractions and integrated rate asymmetries for the rare decays $B \to K^{(*)} l^{+} l^{-}$ , where $l^{+} l^{-}$ is either $e^{+} e^{-}$ or $μ^{+} μ^{-}$ , using a sample of $384 \times 10^{6}$ $B \bar{B}$ 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 $B \to K l^{+} l^{-}$ and $B \to K^{*} l^{+} l^{-}$ which differ, respectively, by $3.2 σ$ and $2.7 σ$ , including systematic uncertainties, from the standard model expectations.