CMB and 21-cm Signals for Dark Matter with a Long-Lived Excited State

Abstract

Motivated by the eXciting Dark Matter (XDM) model of Finkbeiner & Weiner, hypothesized to explain the 511 keV signal in the center of the Milky Way, we consider the CMB and 21-cm signatures of models of dark matter with collisional long-lived excited states. We compute the relic excitation fraction from the early universe for a variety of assumptions about the collisional de-excitation cross-section and thermal decoupling. The relic excitation fraction can be as high as 1% for natural regions of parameter space, but could be orders of magnitude smaller. Since the lifetime of the excited state is naturally greater than 10^13s, we discuss the signatures of such relic excitation on cosmic microwave background (CMB) and high-z 21-cm observations. Such models have potentially richer astrophysical signals than the traditional WIMP annihilations and decays, and may have observable consequences for future generations of experiments.

11 pages, 11 figures, slightly revised, Phys. Rev. D in press

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• Energy Injection And Absorption In The Cosmic Dark Ages
• Direct Detection of Multi-component Secluded WIMPs
• Dark matter-neutrino interactions through the lens of their cosmological implications
• Constraints on dark matter annihilation from CMB observations before Planck
• An X-Ray Line from eXciting Dark Matter
• Constraining dark matter late-time energy injection: decays and p-wave annihilations
• Consistent Scenarios for Cosmic-Ray Excesses from Sommerfeld-Enhanced Dark Matter Annihilation
• PAMELA, DAMA, INTEGRAL and Signatures of Metastable Excited WIMPs
• Self-interacting inelastic dark matter: A viable solution to the small scale structure problems
• Lifetime Constraints for Late Dark Matter Decay
• A Dark Matter Model with Non-Abelian Gauge Symmetry
• Signatures of clumpy dark matter in the global 21 cm background signal
• Nonabelian dark matter models for 3.5 keV X-rays
• The ups and downs of inelastic dark matter: Electron recoils from terrestrial upscattering
• A Model For Late Dark Matter Decay
• Nuclear scattering of dark matter coupled to a new light scalar
• Perturbed Recombination from Dark Matter Annihilation
• Cosmic Microwave Background Constraints on Dark Matter Models of the Galactic Center 511 keV Signal
• MiXDM: Cosmic Ray Signals from Multiple States of Dark Matter
• The Hydrogen Mixing Portal, Its Origins, and Its Cosmological Effects