Radiatively generated neutrino masses in SU(3)L×U(1)N gauge models

In SU(3)L×U(1)N gauge models for electroweak interactions, we discuss how to implement a radiative mechanism of generating Majorana neutrino masses by considering the property that the Higgs scalar, which has a coupling to a charged lepton (ℓ)-neutrino (ν) pair, is naturally included. The mechanism is shown to work in models with a heavy charged lepton, ω+, in a lepton triplet (ν, ℓ, ω+) and with a heavy neutral lepton, N, in (ν, ℓ, N). A minimal model with ℓ and ℓc in (ν, ℓ, ℓc) together with a sextet Higgs scalar suffers from a fine-tuning problem to suppress tree-level neutrino masses.