Multi-Step Cascade Annihilations of Dark Matter and the Galactic Center Excess
Gilly Elor, Nicholas L. Rodd, Tracy R. Slatyer

TL;DR
This paper investigates how multi-step dark-sector cascades in dark matter annihilation can explain the Galactic Center gamma-ray excess, broadening spectral signatures and expanding viable parameter space.
Contribution
It provides a model-independent analysis of multi-step dark-sector cascades and their impact on gamma-ray spectra, highlighting conditions that fit the observed excess.
Findings
Multi-step cascades broaden photon spectra, allowing for heavier dark matter.
Hierarchical cascades favor dark matter masses between 20-150 GeV.
Degenerate cascades can accommodate higher dark matter masses.
Abstract
If dark matter is embedded in a non-trivial dark sector, it may annihilate and decay to lighter dark-sector states which subsequently decay to the Standard Model. Such scenarios - with annihilation followed by cascading dark-sector decays - can explain the apparent excess GeV gamma-rays identified in the central Milky Way, while evading bounds from dark matter direct detection experiments. Each 'step' in the cascade will modify the observable signatures of dark matter annihilation and decay, shifting the resulting photons and other final state particles to lower energies and broadening their spectra. We explore, in a model-independent way, the effect of multi-step dark-sector cascades on the preferred regions of parameter space to explain the GeV excess. We find that the broadening effects of multi-step cascades can admit final states dominated by particles that would usually produce…
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Taxonomy
TopicsDark Matter and Cosmic Phenomena · Computational Physics and Python Applications · Cosmology and Gravitation Theories
