Abstract :
We consider an image dark sector, parallel to the image ordinary sector. The hypercharges, baryon numbers and lepton numbers in the dark sector are opposite to those in the ordinary sector. We further introduce three types of messenger sectors: (i) two or more gauge-singlet Dirac fermions, (ii) two or more image-bidoublet Higgs scalars, (iii) at least one gauge-singlet Dirac fermion and at least one image-bidoublet Higgs scalar. The lepton number conserving decays of the heavy fermion singlet(s) and/or Higgs bidoublet(s) can simultaneously generate a lepton asymmetry in the image-doublet leptons and an opposite lepton asymmetry in the image-doublet leptons to account for the cosmological baryon asymmetry and dark matter relic density, respectively. The lightest dark nucleon as the dark matter particle should have a mass about 5 GeV. By integrating out the heavy fermion singlet(s) and/or Higgs bidoublet(s), we can obtain three light Dirac neutrinos composed of the ordinary and dark neutrinos. If a mirror symmetry is further imposed, our models will not require more unknown parameters than the traditional type-I, type-II or type-I+II seesaw models.
