https://doi.org/10.1140/epjc/s10052-025-14546-7
Regular Article - Theoretical Physics
Pseudo-Dirac sterile neutrino dark matter
1
Department of Physics, Center for Advanced Quantum Studies, Beijing Normal University, 100875, Beijing, China
2
Department of Physics, Northeastern University, 02115-5000, Boston, MA, USA
3
CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100190, Beijing, China
4
School of Physics, University of Chinese Academy of Sciences, 100049, Beijing, China
5
School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS, 310024, Hangzhou, China
6
International Centre for Theoretical Physics Asia-Pacific, Beijing/Hangzhou, China
7
Key Laboratory of Multi-scale Spin Physics, Ministry of Education, Beijing Normal University, 100875, Beijing, China
8
National Astronomical Observatories, Chinese Academy of Sciences, 100012, Beijing, China
9
Institute of Theoretical Physics, Chinese Academy of Sciences, 100190, Beijing, China
10
University of Chinese Academy of Sciences, 100190, Beijing, China
Received:
31
October
2024
Accepted:
18
July
2025
Published online:
7
August
2025
Sterile neutrino is a promising dark matter (DM) candidate. However, the parameter space of this scenario has almost been ruled out by the X-ray observation results whenever the sterile neutrino is solely produced by the Dodelson–Widrow (DW) mechanism in the early Universe. In this letter, we propose an extension to the minimal sterile neutrino DM model by introducing the pseudo-Dirac sterile neutrino, which implies the existence of two nearly degenerate Majorana states 
, and a permutation symmetry. The heavy state 
is produced via the DW mechanism, and the light state 
, which serves as the DM, is produced from the decay of in the early Universe. The X-ray constraint is avoided by the permutation symmetry, which forbids the two-body decay of the DM into active neutrinos and photons. A promising signal of this scenario is the effective number of neutrino species, which will be precisely measured in future experiments, such as CMB stage IV. We further study the impact of this model on the cosmological parameters. The Markov Chain Monte Carlo analysis for the Planck + BAO + R19 data gives 
, which may relieve the Hubble tension.
© The Author(s) 2025
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