Lepton flavor violation (LFV) has been observed in neutrino oscillations. For charged lepton FV decays only upper limits are known, but sizable branching ratios are expected in many neutrino mass models. High scale models, such as the classical supersymmetric seesaw, usually predict that decays li→3lj are roughly a factor α maller than the corresponding decays li→ljγ. Here we demonstrate that the Z0-penguin diagram can give an enhancement for decays li→3lj in many extensions of the MSSM. We first discuss why the Z0-penguin is not dominant in the MSSM with seesaw and show that much larger contributions from the Z0-penguin are expected in general. We then demonstrate the effect numerically in two example models, namely, the supersymmetric inverse seesaw and R-parity violating supersymmetry.
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