Cosmic-Ray Signatures of Annihilating and Semi-Annihilating Dark Matter via One-Step Cascades
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arXiv
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| Format: | Preprint |
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2026
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| author | D'Eramo, Francesco Manconi, Silvia Sassi, Tommaso |
| author_facet | D'Eramo, Francesco Manconi, Silvia Sassi, Tommaso |
| contents | We present a framework in which three classes of dark matter number-changing processes can affect both the relic abundance via thermal freeze-out in the early universe and the generation of indirect cosmic-ray signals today. These processes are: (i) direct annihilations into Standard Model final states; (ii) annihilations into metastable on-shell mediators that subsequently decay into Standard Model particles; (iii) semi-annihilation processes featuring a dark matter particle in the final state, accompanied by a metastable mediator. A central element of our analysis is the systematic inclusion of semi-annihilation alongside the more commonly considered channels. This setup is largely model-independent, as we only assume the presence of one or more of these processes with unsuppressed $s$-wave contributions. We analyze representative benchmarks for the dominant decay modes of the mediator and show how the resulting injection spectra for $γ$ rays, neutrinos, and cosmic-ray antimatter vary with the relative importance of the three classes of processes. As an application, we evaluate the observable $γ$-ray fluxes from dwarf spheroidal galaxies in the GeV-TeV window. Finally, we provide explicit model realizations in which multiple processes coexist, and discuss how their interplay shapes indirect detection signatures. Our results provide a consistent connection between early-universe dynamics and present-day observables, revealing distinctive features that arise when multiple dark matter processes contribute simultaneously. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_21976 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Cosmic-Ray Signatures of Annihilating and Semi-Annihilating Dark Matter via One-Step Cascades D'Eramo, Francesco Manconi, Silvia Sassi, Tommaso High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena We present a framework in which three classes of dark matter number-changing processes can affect both the relic abundance via thermal freeze-out in the early universe and the generation of indirect cosmic-ray signals today. These processes are: (i) direct annihilations into Standard Model final states; (ii) annihilations into metastable on-shell mediators that subsequently decay into Standard Model particles; (iii) semi-annihilation processes featuring a dark matter particle in the final state, accompanied by a metastable mediator. A central element of our analysis is the systematic inclusion of semi-annihilation alongside the more commonly considered channels. This setup is largely model-independent, as we only assume the presence of one or more of these processes with unsuppressed $s$-wave contributions. We analyze representative benchmarks for the dominant decay modes of the mediator and show how the resulting injection spectra for $γ$ rays, neutrinos, and cosmic-ray antimatter vary with the relative importance of the three classes of processes. As an application, we evaluate the observable $γ$-ray fluxes from dwarf spheroidal galaxies in the GeV-TeV window. Finally, we provide explicit model realizations in which multiple processes coexist, and discuss how their interplay shapes indirect detection signatures. Our results provide a consistent connection between early-universe dynamics and present-day observables, revealing distinctive features that arise when multiple dark matter processes contribute simultaneously. |
| title | Cosmic-Ray Signatures of Annihilating and Semi-Annihilating Dark Matter via One-Step Cascades |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2604.21976 |