When Freeze-out occurs due to a non-Boltzmann suppression: A study of degenerate dark sector
| Autor: | Biswas, Anirban, Ganguly, Sougata, Roy, Sourov |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | JHEP06(2021)108 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1007/JHEP06(2021)108 |
| Popis: | Exponential suppression or commonly known as the Boltzmann suppression in the number density of dark matter is the key ingredient for creating chemical imbalance prior to the usual thermal freeze-out. A degenerate/quasi-degenerate dark sector can experience a different exponential suppression in the number density analogous to the radioactive decay law leading to a delayed freeze-out mechanism of dark matter known as the co-decaying dark matter. In this work, we study the dynamics of a multicomponent dark matter from thermally decoupled degenerate dark sector in a hidden U$(1)_{X}$ extension of the Standard Model. We compute the relic density of dark matter frozen-out through the co-decaying mechanism by solving four coupled Boltzmann equations. We demonstrate how temperature $T^\prime $ of the dark sector changes due to all types of $3\rightarrow 2$ and $2\rightarrow 2$ interactions along with the eternal expansion of the Universe. We find that $3\rightarrow 2$ interactions enhance $T^\prime$ by producing energetic particles in the dark sector while the excess heat is transferred by $2\rightarrow 2$ interactions to the entire dark sector. As the direct detection is possible only through the feeble portal couplings, we investigate the neutrino and $\gamma$-ray signals from dark matter annihilation via one step cascade processes and compare our results with the measured fluxes of atmospheric neutrinos by Super-Kamiokande and diffuse $\gamma$-rays by Fermi-LAT, EGRET, INTEGRAL collaborations. We find that the present scenario easily evades all the existing bounds from atmospheric neutrino and diffuse $\gamma$-ray observations for degenerate dark sector. However, the constraints are significant for quasi degenerate scenario. Comment: 65 pages, 25 figures, 2 tables, additional indirect detection constraints are included, new references are added, conclusion remains unchanged, version matches with the published version in JHEP |
| Databáze: | arXiv |
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