Phenomenology of the simplest linear seesaw mechanism

Abstract

The linear seesaw mechanism provides a simple way to generate neutrino masses. In addition to Standard Model particles, it includes quasi-Dirac leptons as neutrino mass mediators, and a leptophilic scalar doublet seeding small neutrino masses. Here we review its associated physics, including restrictions from theory and phenomenology. The model yields potentially detectable $\mu \to e\gamma$ rates as well as distinctive signatures in the production and decay of heavy neutrinos ($N_i$) and the charged Higgs boson ($H^{\pm }$) arising from the second scalar doublet. We have found that production processes such as $e^{+}{e}^{-}\to NN$, $e^{-}\gamma \to N{H}^{-}$ and $e^{+}{e}^{-}\to H^{+}{H}^{-}$ followed by the decay chain $H^{\pm }\to {\ell }_i^{\pm }N$, $N\to {\ell }_j^{\pm }{W}^{\mp }$ leads to striking lepton number violation signatures at high energies which may probe the Majorana nature of neutrinos.

Comments: 53 pages, 33 figures, 2 tables, Matches published version