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Astrophysical signatures of secluded dark matter

2008; Elsevier BV; Volume: 671; Issue: 3 Linguagem: Inglês

10.1016/j.physletb.2008.12.012

1873-2445

Maxim Pospelov, Adam Ritz,

Cosmology and Gravitation Theories

We analyze the indirect astrophysical signatures of secluded models of WIMP dark matter, characterized by a weak-scale rate for annihilation into light MeV-scale mediators which are metastable to decay into Standard Model states. Such scenarios allow a significant enhancement of the annihilation cross section in the galactic halo relative to its value at freeze-out, particularly when the mediator is light enough for this process to proceed through radiative capture to a metastable `WIMP-onium' bound state. For MeV-scale vector mediators charged under a hidden U(1)' gauge group, the enhanced annihilation rate leads predominantly to a sizable excess positron flux, even in the absence of astrophysical boost factors.