Self-interacting dark matter with observable $ΔN_{\rm eff}$
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866908334684110848 |
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| author | Borah, Debasish Mahapatra, Satyabrata Sahu, Narendra Thounaojam, Vicky Singh |
| author_facet | Borah, Debasish Mahapatra, Satyabrata Sahu, Narendra Thounaojam, Vicky Singh |
| contents | We propose a GeV-scale self-interacting dark matter (SIDM) candidate within a dark $U(1)_D$ gauged extension of the Standard Model (SM), addressing small-scale structure issues in $Λ$CDM while predicting an observable contribution to $ΔN_{\rm eff}$ in the form of dark radiation. The model introduces a fermionic DM candidate $χ$ and a scalar $ϕ$, both charged under an unbroken $U(1)_D$ gauge symmetry. The self-interactions of $χ$ are mediated by a light vector boson $X^μ$, whose mass is generated via the Stueckelberg mechanism. The relic abundance of $χ$ is determined by thermal freeze-out through annihilations into $X^μ$, supplemented by a non-thermal component from the late decay of $ϕ$. Crucially, $ϕ$ decays after the Big Bang Nucleosynthesis (BBN) but before the Cosmic Microwave Background (CMB) epoch, producing additional $χ$ and a dark radiation species ($ν_S$). This late-time production compensates for thermal underabundance due to efficient annihilation into light mediators, while remaining consistent with structure formation constraints. The accompanying dark radiation yields a detectable $ΔN_{\rm eff}$, compatible with Planck 2018 bounds and within reach of next-generation experiments such as SPT-3G, CMB-S4, and CMB-HD. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_16910 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Self-interacting dark matter with observable $ΔN_{\rm eff}$ Borah, Debasish Mahapatra, Satyabrata Sahu, Narendra Thounaojam, Vicky Singh High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics We propose a GeV-scale self-interacting dark matter (SIDM) candidate within a dark $U(1)_D$ gauged extension of the Standard Model (SM), addressing small-scale structure issues in $Λ$CDM while predicting an observable contribution to $ΔN_{\rm eff}$ in the form of dark radiation. The model introduces a fermionic DM candidate $χ$ and a scalar $ϕ$, both charged under an unbroken $U(1)_D$ gauge symmetry. The self-interactions of $χ$ are mediated by a light vector boson $X^μ$, whose mass is generated via the Stueckelberg mechanism. The relic abundance of $χ$ is determined by thermal freeze-out through annihilations into $X^μ$, supplemented by a non-thermal component from the late decay of $ϕ$. Crucially, $ϕ$ decays after the Big Bang Nucleosynthesis (BBN) but before the Cosmic Microwave Background (CMB) epoch, producing additional $χ$ and a dark radiation species ($ν_S$). This late-time production compensates for thermal underabundance due to efficient annihilation into light mediators, while remaining consistent with structure formation constraints. The accompanying dark radiation yields a detectable $ΔN_{\rm eff}$, compatible with Planck 2018 bounds and within reach of next-generation experiments such as SPT-3G, CMB-S4, and CMB-HD. |
| title | Self-interacting dark matter with observable $ΔN_{\rm eff}$ |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2504.16910 |