Self-Scattering for Dark Matter with an Excited State

Abstract

Self-interacting dark matter scenarios have recently attracted much attention, as a possible means to alleviate the tension between N-body simulations and observations of the dark matter distribution on galactic and sub-galactic scales. The presence of internal structure for the dark matter --- for example, a nearly-degenerate state in the spectrum that could decay, or be collisionally excited or de-excited --- has also been proposed as a possible means to address these discrepancies. Such internal structure can be a source of interesting signatures in direct and indirect dark matter searches, for example providing a novel explanation for the 3.5 keV line recently observed in galaxies and galaxy clusters. We analyze a simple model of dark matter self-scattering including a nearly-degenerate excited state, and develop an accurate analytic approximation for the elastic and inelastic s-wave cross sections, which is valid outside the perturbative regime provided the particle velocity is sufficiently low (this condition is also required for the s-wave to dominate over higher partial waves). We anticipate our results will be useful in incorporating inelastic self-scattering into N-body simulations, in order to study the quantitative impact of nearly-degenerate states in the dark matter spectrum on galactic structure and dynamics, and in computing the indirect signatures of multi-state dark matter.

27 pages + 19 pages appendices, 14 figures, Submitted to JCAP. v2 fixes typos, adds three references

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Cited by in corpus (6)

• Self-interacting inelastic dark matter: A viable solution to the small scale structure problems
• Self-interacting Dark Matter Without Direct Detection Constraints
• Heating Neutron Stars with Inelastic Dark Matter and Relativistic Targets
• Astrophysical probes of inelastic dark matter with a light mediator
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