Effects of bound states on dark matter annihilation

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Physical Review D

DOI:https://doi.org/10.1103/PhysRevD.93.115020· OSTI ID:1596467

An, Haipeng ^[1]; Wise, Mark B. ^[1]; Zhang, Yue ^[1]

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1. California Inst. of Technology (CalTech), Pasadena, CA (United States)

Here, we study the impact of bound state formation on dark matter annihilation rates in models where dark matter interacts via a light mediator, the dark photon. We derive the general cross section for radiative capture into all possible bound states, and point out its nontrivial dependence on the dark matter velocity and the dark photon mass. For indirect detection, our result shows that dark matter annihilation inside bound states can play an important role in enhancing signal rates over the rate for direct dark matter annihilation with Sommerfeld enhancement. The results are strongest for large dark gauge coupling and when the dark photon mass is smaller than the typical momentum of dark matter in the Galaxy. As an example, we show that for thermal dark matter the Fermi gamma ray constraint is substantially increased once bound state effects are taken into account. We also find that bound state effects are not important for dark matter annihilation during the freeze-out and recombination epochs.

• Research Organization: California Institute of Technology (CalTech), Pasadena, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); Gordon and Betty Moore Foundation
• Grant/Contract Number: SC0011632; FG02-92ER40701; SC0010255
• OSTI ID: 1596467
• Alternate ID(s): OSTI ID: 1257496
• Journal Information: Physical Review D, Vol. 93, Issue 11; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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79 ASTRONOMY AND ASTROPHYSICS