Inverse tribimaximal type-III seesaw mechanism and lepton flavor violation

Abstract

We present a type-III version of inverse seesaw or, equivalently an inverse version of type-III seesaw. Naturally small neutrino masses arise at low-scale from the exchange of neutral fermions transforming as hyperchargeless $SU(2)$ triplets. In order to implement tribimaximal lepton mixing we supplement the minimal $SU(3)\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}U(1)$ gauge symmetry with an ${A}_{4}$-based flavor symmetry. Our scenario induces lepton flavor violating (LFV) ${l}_{i}\ensuremath{\rightarrow}{l}_{j}{\overline{l}}_{k}{l}_{m}$ decays that can proceed at the tree level, while radiative ${l}_{i}\ensuremath{\rightarrow}{l}_{j}\ensuremath{\gamma}$ decays and mu-e conversion in nuclei are also expected to be sizeable. LFV decays are related by the underlying flavor symmetry and the new fermions are also expected to be accessible for study at the LHC.