@article{oai:kanazawa-u.repo.nii.ac.jp:00058378, author = {末松, 大二郎 and Aristizabal, Sierra D. and Kubo, Jisuke and Suematsu, Daijiro and Restrepo, D. and Zapata, Oscar}, issue = {1}, journal = {Physical Review D - Particles, Fields, Gravitation and Cosmology}, month = {}, note = {Extending the standard model with three right-handed neutrinos (Nk) and a second Higgs doublet (η), odd under the discrete parity symmetry Z2, Majorana neutrino masses can be generated at one-loop order. In the resulting model, the lightest stable particle, either a boson or a fermion, might be a dark matter candidate. Here we assume a specific mass spectrum (M1 M2