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 μ → eγ rates as well as distinctive signatures in the production and decay of heavy neutrinos (Ni) and the charged Higgs boson (H±) arising from the second scalar doublet. We have found that production processes such as e+e−→ NN, e−γ → NH− and e+e−→ H+H− followed by the decay chain $$ {H}^{\pm}\to {\ell}_i^{\pm }N $$ H ± → ℓ i ± N , $$ N\to {\ell}_j^{\pm }{W}^{\mp } $$ N → ℓ j ± W ∓ leads to striking lepton number violation signatures at high energies which may probe the Majorana nature of neutrinos.

Three-loop inverse scotogenic seesaw models

“…These heavy sterile neutrinos mix with the active ones, with mixing angles of the order of 1 √ 2m N (m νD ) in with i = 1, 2, 3 and n = 1, 2. The admixture of the heavy sterile neutrinos in the left-handed charged current SU(2) L ⊗ U(1) Y weak interaction gives rise to the decay l i → l j γ at one-loop level, with a branching ratio given by [32,[56][57][58][59][60][61][62] Br…”