Seesaw Dirac neutrino mass through dimension-6 operators

Abstract

In this paper, a followup of arXiv: 1802.05722, we describe the many pathways to generate Dirac neutrino mass through dimension-6 operators. By using only the Standard Model Higgs doublet in the external legs one gets a unique operator $\frac{1}{Λ^2} \, \bar{L}\, \barΦ \, \barΦ \, Φ\, ν_R $. In contrast, the presence of new scalars implies new possible field contractions, which greatly increase the number of possibilities. Here we study in detail the simplest ones, involving $SU(2)_L$ singlets, doublets and triplets. The extra symmetries needed to ensure the Dirac nature of neutrinos can also be responsible for stabilizing dark matter.

21 pages, 18 figures