Loop suppression of Dirac neutrino mass in the neutrinophilic two-Higgs-doublet model

We extend the scalar sector of the neutrinophilic two-Higgs-doublet model, where small masses of Dirac neutrinos are obtained via a small vacuum expectation value vν of the neutrinophilic SU(2)L-doublet scalar field which has a Yukawa interaction with only right-handed neutrinos. A global U(1)X symmetry is used for the neutrinophilic nature of the second SU(2)L-doublet scalar field and also for eliminating Majorana mass terms of neutrinos. By virtue of an appropriate assignment of the U(1)X-charges to new particles, our model has an unbroken Z2 symmetry, under which the lightest Z2-odd scalar boson can be a dark matter candidate. In our model, vν is generated by the one-loop diagram to which Z2-odd particles contribute. We briefly discuss a possible signature of our model at the LHC.