Singlet Fermion Assisted Dominant Seesaw with Lepton Flavor and Number Violations and Leptogenesis

Understand

In a recent review Mohapatra has discussed how type-I seesaw mechanism suppressed by fine tuning of Yukawa couplings, or specific textures of associated fermion mass matrices, can form the basis of neutrino masses in TeV scale $W_R$ boson models.

• In this paper we review recent works in another class of theories where the added presence of fermion singlets manifesting as sterile neutrinos render the type-I seesaw contribution vanishing but extended seesaw dominant where the light neutrino mass formula is same as the classic inverse seesaw but all massive neutrinos are Majorana fermions.
• We also show domunance of linear seesaw, or double seesaw, or type-II seesaw in due to cancellation of type-I seesaw.
• Embeddings of this mechnism in supersymmetric as well as non-supersymmetric SO(10) with low or intermediate masses of $W_R$ or $Z_R$ bosons are discussed.