2026/06/30 by Boris Betancourt Kamenetskaia, Mathias Garny, Alejandro Ibarra +2
Physics and Astronomy · #hep-ph
12 pages, 4 figures
arxiv created 2026/07/30 · arxiv updated 2026/07/31
The growth of primordial density fluctuations in the early Universe leads to an inhomogeneous dark matter distribution at high redshift, where semi-annihilation processes of the form χχ→ χc ϕ, with ϕ being dark radiation, can occur with a sizable rate. Using a state-of-the-art model for the cosmological boost factor, we compute the resulting redshift-dependent flux of boosted dark matter particles generated by semi-annihilation, and we study the implications of the boosted component for structure formation and direct detection experiments. We find a model independent upper limit on the semi-annihilation cross-section from structure formation, which reads ⟨σ2→1 v⟩≤4.2×10-19~(mχ/1~\rm GeV)~cm3/\rm s. Further, we find that the cosmological contribution to the boosted dark matter flux can be comparable to the galactic one, providing an O(1) enhancement to the sensitivity of dark matter searches, thus slightly enhancing the discovery potential in direct detection experiments of semi-annihilation scenarios where the dark matter interacts with the nucleus.