Abstract
We propose a way to generate tiny couplings of freeze-in massive particle dark matter with the Standard Model particles dynamically by considering an extension of the electroweak gauge symmetry. The dark matter is considered to be a singlet under this extended gauge symmetry which we have assumed to be the one in a very widely studied scenario called left-right symmetric model. Several heavy particles, that can be thermally inaccessible in the early Universe due to their masses being greater than the reheat temperature after inflation, can play the role of portals between dark matter and Standard Model particles through one loop couplings. Due to the loop suppression, one can generate the required non-thermal dark matter couplings without any need of highly fine tuned Yukawa couplings beyond that of electron Yukawa with the Standard Model like Higgs boson. We show that generic values of Yukawa couplings as large as $\mathcal{O}(0.01)$ to $\mathcal{O}(1)$ can keep the dark matter out of thermal equilibrium in the early Universe and produce the correct relic abundance later through the freeze-in mechanism. Though the radiative couplings of dark matter are tiny as required by the freeze-in scenario, the associated rich particle sector of the model can be probed at ongoing and near future experiments. The allowed values of dark matter mass can remain in a wide range from keV to TeV order keeping the possibilities of warm and cold dark matter equally possible.
Highlights
In view of several astrophysical and cosmological evidences, the existence of nonbaryonic form of matter, or the so-called dark matter (DM) in large amount in the present Universe has become an irrefutable fact
We have proposed a UV complete framework to dynamically generate tiny couplings required for nonthermal dark matter scenarios whose relic abundance is generated through the freeze-in mechanism, within the framework called freeze-in massive particle
Based on gauge symmetric extensions of the standard model, we consider the left-right symmetric model which have several other motivations related to the origin of parity violation, neutrino mass among others
Summary
In view of several astrophysical and cosmological evidences, the existence of nonbaryonic form of matter, or the so-called dark matter (DM) in large amount in the present Universe has become an irrefutable fact. One of the viable alternatives of WIMP paradigm, which may be a possible reason of null results at various direct detection experiments, is to consider the nonthermal origin of DM [15] In this scenario, the initial number density of DM in the early Universe is negligible and it is assumed that the interaction strength of DM with other particles in the thermal bath is so feeble that it never reaches thermal equilibrium at any epoch in the early Universe. One of the possible explanation of such feeble interactions is to consider DM to be connected to the visible sector via nonrenormalizable higher dimensional effective operators This results in a different type of freeze-in mechanism known as UV-freeze-in [15,27,28], where the comoving number density of DM is directly proportional to reheat temperature TRH of the Universe and sensitive to the early Universe cosmology.
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