Probing New Physics through mu-e Universality in K->lnu
Abstract
The recent NA48/2 improvement on RK=Gamma(K->e nue)/Gamma(K->mu numu) emphasizes the role of Kl2 decays in probing the mu-e universality. Supersymmetric (SUSY) extensions of the Standard Model can exhibit mu-e non-universal contributions. Their origin is twofold: those deriving from lepton flavor conserving couplings are subdominant with respect to those arising from lepton flavor violating (LFV) sources. We show that mu-e non-universality in Kl2 is quite effective in constraining relevant regions of SUSY models with LFV (for instance, supergravities with a see-saw mechanism for neutrino masses). A comparison with analogous bounds coming from tau LFV decays proves the relevance of the measurement of RK to probe LFV in SUSY.
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