Abstract
We consider the thermal effects into the evaluation of the dark matter production process. With the assistance of the right handed neutrinos, the freeze-in massive particle dark matter production history can be modified by the two-step phase transitions. The kinematic of decay/inverse decay or annihilation processes can be affected by the finite temperature effects as the Universe cools down. The history of the symmetry respected by the model can be revealed by the DM relic abundance evolution processes. The strong first order electroweak phase transition generated gravitational waves can be probed. The number of extra scalars for the Hierarchy problem can be probed through the Higgs off-shell searches at the LHC.
Highlights
Tfo ∼ mDM /26 where the DM particles decouple from the thermal plasma
We implement the thermal history of symmetry change with the Universe cools down into the dark matter production history
With the assistance of right handed sterile neutrino that lives in thermal bath when the feebly interacting massive particle (FIMP) DM is producing, the dark matter production process can be multi-step due to the effects of the EWPT
Summary
We utilize the model similar to refs. [14, 20, 22, 23]. It contains a Z2-odd majorana fermion χ and a real-scalar boson φ. The sterile neutrino-Higgs-lepton boublet couplings in the pseudo-Dirac case can be in a much wider range than the couplings in the majorana case, and the freeze-in process is not much disturbed by details of the sterile-neutrino sector. We only introduce one pseudo-Dirac sterile-neutrino in our calculations, and this seems to be different from some common see-saw models, we can always rotate the mass basis in the mN,D ∝ I case so that only one sterile neutrino interact with the dark matter, see appendix A. The “pseudo-Dirac” particle with the nonzero μ1,2 and yNCi terms split into two nearly-degenerate majorana components These terms are usually rather small in both the linear- and inverse-seesaw models, and their effects in the early universe are usually negligible. For convenience, we just set all of them to be zero during the calculation processes
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