Dark sector freeze-out due to a non-Boltzmann suppression
November 21, 2022
June 15, 2023
The well-known Boltzmann suppression is the key ingredient
to create chemical imbalance for thermal dark matter. In
a degenerate/quasi-degenerate dark sector chemical imbalance
can also be generated from a different mechanism which is analogous
to the radioactive decay law, known as co-decaying dark matter.
In this work, we have studied the dynamics of a multicomponent
thermally decoupled degenerate dark sector in a hidden $U(1)_X$ extension
of the Standard Model. We compute the relic density and the temperature ($T^\prime$)
evolution of the hidden sector by considering all possible $2\rightarrow2$
and $3\rightarrow2$ processes. We find that the production of energetic particles
from $3\rightarrow2$ processes increase the temperature of the dark sector whereas
the rate of growth of temperature is decelerated due to the presence of $2\rightarrow2$
processes and expansion of the Universe. We also study the prospect of detecting
neutrino and $\gamma$-ray signals from DM annihilation via one step cascade processes.
We find that in the present scenario, all the existing indirect detection constraints
arising from measured fluxes of atmospheric neutrinos by Super-Kamiokande and diffuse
$\gamma$-rays by EGRET, Fermi-LAT, and INTEGRAL can easily be evaded
for the degenerate dark sector. However for the quasi degenerate scenario the
constraints are significant.
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