Self-Interacting Sterile Neutrino Cold Dark Matter: Resonant Production Mechanism in the Early Universe
Abstract
Sterile neutrinos are well-motivated dark matter candidates, but their conventional production through active-sterile mixing is tightly constrained by X-ray searches and structure-formation observations. We propose a distinct production mechanism operating entirely within a sterile sector: two sterile neutrinos, N1 and N2, coupled to a singlet scalar ϕ, with N1 the dark matter candidate and N2 held in equilibrium through frequent scattering induced by its scalar interaction. Thermal self-energies induced by the N2 and ϕ backgrounds generate both a temperature-dependent mass splitting and an off-diagonal mixing between N1 and N2. As the Universe cools, the in-medium levels can undergo a level crossing, leading to resonantly enhanced conversion of the thermal N2 population into N1. We formulate the conversion using a density-matrix kinetic equation that consistently incorporates coherent N1-N2 conversion, collisional decoherence, and thermal repopulation of N2. For a narrow resonance, the integrated conversion probability admits a simple analytic form that coincides with the Landau-Zener result, despite the underlying collisionally damped dynamics. In the weak-conversion regime relevant for freeze-in, this correspondence provides a robust analytic description of the resonant production. We derive the resulting dark matter abundance and identify the conditions for cosmological stability of N1 and for resonant conversion to dominate over direct scattering and decay production. The resulting relic abundance scales as Y1∝ g122 g22MPl/m1, making the dark matter energy density approximately independent of m1. This mechanism provides a new route to sterile-neutrino dark matter that does not require appreciable active-sterile mixing.
Related
- Early Universe production of W bosons in neutrino decays
- Natural Saturation Of The Sterile Neutrino Dark Matter Resonant Production By a High Lepton Flavor Asymmetry In Primordial Plasma
- Resonant Dynamics of Gravitational Wave and Chiral Alfvén wave in the Early Universe
- A New Probe of Strongly-Interacting Dark Sector using Neutrino Telescopes
- SN1987A constraints on the neutrino-dark-fermion interaction from resonant scattering with CνB
BibTeX
@misc{chun2026selfinteracting,
title = {{Self-Interacting Sterile Neutrino Cold Dark Matter: Resonant Production Mechanism in the Early Universe}},
author = {Eung Jin Chun and Kenji Kadota and Seokhoon Yun},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04650},
eprint = {2609.04650},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04650},
}
RIS
TY - UNPB
TI - Self-Interacting Sterile Neutrino Cold Dark Matter: Resonant Production Mechanism in the Early Universe
AU - Eung Jin Chun
AU - Kenji Kadota
AU - Seokhoon Yun
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.04650
UR - https://arxiv.org/abs/2609.04650
AB - Sterile neutrinos are well-motivated dark matter candidates, but their conventional production through active-sterile mixing is tightly constrained by X-ray searches and structure-formation observations. We propose a distinct production mechanism operating entirely within a sterile sector: two sterile neutrinos, N_1 and N_2, coupled to a singlet scalar ϕ, with N_1 the dark matter candidate and N_2 held in equilibrium through frequent scattering induced by its scalar interaction. Thermal self-energies induced by the N_2 and ϕ backgrounds generate both a temperature-dependent mass splitting and an off-diagonal mixing between N_1 and N_2. As the Universe cools, the in-medium levels can undergo a level crossing, leading to resonantly enhanced conversion of the thermal N_2 population into N_1. We formulate the conversion using a density-matrix kinetic equation that consistently incorporates coherent N_1-N_2 conversion, collisional decoherence, and thermal repopulation of N_2. For a narrow resonance, the integrated conversion probability admits a simple analytic form that coincides with the Landau-Zener result, despite the underlying collisionally damped dynamics. In the weak-conversion regime relevant for freeze-in, this correspondence provides a robust analytic description of the resonant production. We derive the resulting dark matter abundance and identify the conditions for cosmological stability of N_1 and for resonant conversion to dominate over direct scattering and decay production. The resulting relic abundance scales as Y_1∝ g_12^2 g_22M_Pl/m_1, making the dark matter energy density approximately independent of m_1. This mechanism provides a new route to sterile-neutrino dark matter that does not require appreciable active-sterile mixing.
ER -