Abstract
Dark Matter can form bound states upon the emission of quanta of energy equal to the binding energy. The rate of this process is large for strongly-interacting Dark Matter, and further enhanced by long distance effects. The resulting monochromatic and diffuse $\gamma$-rays can be tested in indirect detection experiments. If Dark Matter has electroweak charge, indirect signals include multiple observable photon lines for masses in the TeV range. Else if it couples only via a dark photon portal, diffuse spectra from dwarf galaxies and CMB reionization set powerful limits for masses below a TeV. This mechanism provides a powerful means of probing Asymmetric Dark Matter today.
Highlights
Having no annihilation rate today, asymmetric dark matter (DM) is largely untestable in indirect-detection experiments absent some nonminimal assumption
We argue in a compelling analogy with Standard Model (SM) baryons that “nucleons” of a dark strong sector naturally emit a light particle on forming bound-state “nuclei.” The rate for this process is calculable semianalytically in the limit of shallow bound states, and can be large, allowing us to probe dark nuclear asymmetric DM in existing indirect-detection experiments. (See [3,4,5,6,7] for related work)
In this paper we studied the indirect-detection signal associated with the formation of bound states of DM, due to the emission of quanta with energy equal to the binding energy of the bound state
Summary
Having no annihilation rate today, asymmetric dark matter (DM) is largely untestable in indirect-detection experiments absent some nonminimal assumption (e.g., a remnant annihilating component, or decaying relic, see [1,2] for reviews on the subject). The dark sector is roughly characterized at low energies by (i) the mass of the lightest dark baryon, M, which constitutes the DM; (ii) the mass of the “dark pion,” Mπ ≲ M, that sets the typical range for nuclear interactions amongst the baryons (we assume that this state is cosmologically unstable); and (iii) the mass of a weakly coupled mediator external to the strong sector, MV, e.g., SM gauge bosons. The first is automatically realized if DM has electroweak charges, and gives rise to emission of SM gauge bosons, in particular, to monochromatic photons. These are constrained by observations of the Galactic Center by FERMI and HESS. As we will discuss shortly, both alternatives can be analyzed by exploiting the analogy with deuterium production in the SM, yet they present very different experimental signatures
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