Minimal lepton flavor violating realizations of minimal seesaw models
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We study the implications of the global U(1) R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. In the context of minimal type I seesaw scenarios with a slightly broken U(1) R , we show that, depending on the R-charge assignments, two classes of generic models can be identified. Models where the right-handed neutrino masses and the lepton number breaking scale are decoupled, and models where the parameters that slightly break the U(1) R induce a suppression in the light neutrino mass matrix. We show that within the first class of models, contributions of right-handed neutrinos to charged lepton flavor violating processes are severely suppressed. Within the second class of models we study the charged lepton flavor violating phenomenology in detail, focusing on μ → eγ, μ → 3e and μ − e conversion in nuclei. We show that sizable contributions to these processes are naturally obtained for right-handed neutrino masses at the TeV scale. We then discuss the interplay with the effects of the right-handed neutrino interactions on primordial B − L asymmetries, finding that sizable right-handed neutrino contributions to charged lepton flavor violating processes are incompatible with the requirement of generating (or even preserving preexisting) B − L asymmetries consistent with the observed baryon asymmetry of the Universe.
KeywordsRare Decays Beyond Standard Model Neutrino Physics