Radiative generation of lepton masses with the U(1)′ gauge symmetry

We revisit our previous model proposed by Okada and Yagyu [Phys. Rev. D 89, 053008 (2014)], in which lepton masses, except the tauon mass, are generated at the one-loop level in TeV-scale physics. Although in the previous work, rather large Yukawa coupling constants, i.e., greater than about 3, are required to reproduce the muon mass, we do not need to introduce such large O(1) couplings. In our model, masses for neutrinos (charged leptons) are generated by higher-dimensional operators with two isospin triplet (singlet and doublet) scalar fields, which are introduced at the one-loop level. Thus, the mass hierarchy between neutrinos and charged leptons can be naturally described by the difference in the number of vacuum expectation values of the triplet fields which must be much smaller than the vacuum expectation values of the doublet field due to the constraint from the electroweak rho parameter. Furthermore, the discrepancy in the measured muon anomalous magnetic moment (g - 2) from the prediction in the standard model is explained by new particle contributions at the one-loop level. The collider phenomenology is discussed, especially focusing on a signature from doubly charged scalar bosons at the LHC.