We present a precise measurement of the ratio R_K = Gamma(Ke2(gamma))/Gamma(Kmu2(gamma)) performed with the KLOE detector. The results are based on data collected at the Frascati e^+e^- collider DAFNE for an integrated luminosity of 2.2 fb^{-1}. We find R_K = (2.493pm0.025_{stat}pm0.019_{syst})times 10^{-5}, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation.
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