Abstract
We discuss aspects of a scenario for co-genesis of matter and dark matter which extends the standard model by adding a fourth generation vector-like lepton doublet and show that if the fourth neutrino is a massive pseudo-Dirac fermion with mass in the few hundred GeV range and mass splitting of about 100 keV, its lighter component can be a viable inelastic dark matter candidate. Its relic abundance is produced by the CP violating out-of-equilibrium decay of the type-II seesaw scalar triplet, which also gives rise to the required baryon asymmetry of the Universe via type-II leptogenesis, thus providing a simultaneous explanation of dark matter and baryon abundance observed today. Moreover, the induced vacuum expectation value of the same scalar triplet is responsible for the sub-eV Majorana masses to the three active neutrinos. A stable fourth generation of neutrinos is elusive at collider, however might be detected by current dark matter direct search experiments.
Highlights
It is usually presumed that a weakly interacting massive particle of mass O(100) GeV can be a good candidate for Dark matter (DM) as its annihilation cross-section σ |v| ≈ 3 × 10−26 cm3/s satisfies the requirement of relic abundance, because it is produced by the standard thermal freeze-out mechanism [3]
In this Letter we study the possibility of adding a vectorlike lepton doublet to the standard model (SM) whose neutral
We want to emphasize that the generated lepton asymmetry in the fourth generation does not get converted to baryon via sphaleron processes since L4 being a vector-like doublet, it does not contribute to the B + L anomaly of the standard model
Summary
The triplet mass scale is superheavy so that its CP violating out-of-equilibrium decay can produce asymmetry simultaneously in the DM and lepton sector and above the electroweak phase transition temperature, the lepton asymmetry for the familiar leptons gets converted to the baryon asymmetry via SU(2)L sphalerons [52] In this case, we want to emphasize that the generated lepton asymmetry in the fourth generation does not get converted to baryon via sphaleron processes since L4 being a vector-like doublet, it does not contribute to the B + L anomaly of the standard model.
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