Minimal radiative Dirac neutrino mass models
Julian Calle (Instituto de Física, Universidad de Antioquia, Calle 70 # 52-21, Apartado Aéreo 1226, Medellín, Colombia); Diego Restrepo (Instituto de Física, Universidad de Antioquia, Calle 70 # 52-21, Apartado Aéreo 1226, Medellín, Colombia); Carlos E. Yaguna (Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Avenida Central del Norte # 39-115, Tunja, Colombia); Óscar Zapata (Instituto de Física, Universidad de Antioquia, Calle 70 # 52-21, Apartado Aéreo 1226, Medellín, Colombia)
Neutrinos may be Dirac particles of which the masses arise radiatively at one loop, naturally explaining their small values. In this work, we show that all the one-loop realizations of the dimension-5 operator to effectively generate Dirac neutrino masses can be implemented by using a single local symmetry: . Since this symmetry is anomalous, new chiral fermions, charged under , are required. The minimal model consistent with neutrino data includes three chiral fermions, two of them with the same lepton number. The next minimal models contain five chiral fermions, and their charges can be fixed by requiring a dark matter candidate in the spectrum. We list the full particle content as well as the relevant Lagrangian terms for each of these models. They are new and simple models that can simultaneously accommodate Dirac neutrino masses (at one loop) and dark matter without invoking any discrete symmetries.