Non-decoupling and lepton number violation in left-right models Original Research Article

We argue that large non-decoupling effects of heavy neutrinos can appear naturally in manifestly left-right symmetric models due to the minimization conditions of the scalar potential and the structure of vevʹs imposed by phenomenology. We derive constraints on off-diagonal light-heavy and heavy-heavy neutrino mixings from the searches for lepton violating decays μ → eγ, μ → ee−e+ and μ − e conversion in nuclei. The most stringent limits come from the latter process because its amplitude shows a quadratic non-decoupling dependence on the heavy neutrino mass. Due to the suppression of right-handed currents by the large WR mass the present experiment are not sensitive to the intergenerational mixings between heavy neutrinos if MWR > 200 TeV.