Physics Letters B | 2021
Double type-II Dirac seesaw accompanied by Dirac fermionic dark matter
Abstract
The $SU(3)_c\\times SU(2)_L \\times U(1)_Y$ standard model is extended by a $U(1)_{B-L}$ gauge symmetry with four right-handed neutrinos. Because of their Yukawa couplings to a Higgs singlet for spontaneously breaking the $U(1)_{B-L}$ symmetry, two right-handed neutrinos can form a Dirac fermion to become a stable dark matter particle. Meanwhile, mediated by additionally heavy Higgs doublet(s) and/or fermion singlet(s), the other two right-handed neutrinos can have a dimension-5 operator with the standard model lepton and Higgs doublets as well as the $U(1)_{B-L}$ Higgs singlet. In association with the sphaleron processes, the interactions for generating the Dirac neutrino masses can also produce the observed baryon asymmetry in the universe.