Indirect Detection Signatures for the Origin of Asymmetric Dark Matter

Abstract

We study the decay signatures of Asymmetric Dark Matter (ADM) via higher dimension operators which are responsible for generating the primordial dark matter (DM) asymmetry. Since the signatures are sensitive both to the nature of the higher dimension operator generating the DM asymmetry and to the sign of the baryon or lepton number that the DM carries, indirect detection may provide a window into the nature of the mechanism which generates the DM asymmetry. We consider in particular dimension-6 fermionic operators of the form ${\mathcal{O}}_{ADM}=X{\mathcal{O}}_{B-L}/M^2$, where ${\mathcal{O}}_{B-L}=u^c{d}^c{d}^c,\ell \ell e^c,q\ell d^c$ (or operators related through a Hermitian conjugate) with the scale $M$ around or just below the GUT scale. We derive constraints on ADM particles both in the natural mass range (around a few GeV), as well as in the range between 100 GeV to 10 TeV. For light ADM, we focus on constraints from both the low energy gamma ray data and proton/anti-proton fluxes. For heavy ADM, we consider $\gamma$-rays and proton/anti-proton fluxes, and we fit $e^{+}/e^{-}$ data from AMS-02 and H.E.S.S. (neglecting the Fermi charged particle fluxes which disagree with AMS-02 below 100 GeV). We show that, although the best fit regions from electron/positron measurement are still in tension with other channels on account of the H.E.S.S. measurement at high energies, compared to an ordinary symmetric dark matter scenario, the decay of DM with a primordial asymmetry reduces the tension. Better measurement of the flux at high energy will be necessary to draw a definite conclusion about the viability of decaying DM as source for the signals.

Constraint from H.E.S.S. for heavy ADM scenario is included. Constraint from anti-proton flux for light ADM scenario is included. Matched to the version of publication

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• Sharing but not Caring: Dark Matter and the Baryon Asymmetry of the Universe
• Confronting recent AMS-02 positron fraction and Fermi-LAT Extragalactic Gamma-Ray Background measurements with gravitino dark matter
• Continuous Flavor Symmetries and the Stability of Asymmetric Dark Matter