Searching for Smoking Gun Signatures of Decaying Dark Matter

Abstract

Clear methods to differentiate between decaying and annihilating dark matter (DM) scenarios are still by and large unavailable. In this note, we study the potential astrophysical signatures of a new class of hidden sector decaying DM models, which can address the recent cosmic ray measurements. Such models may produce primary photons and/or neutrinos at large rates, correlated with the leptonic production. The photon and neutrino spectra will then contain sharp features at the TeV scale. We demonstrate the discovery potential for upcoming and future measurements by FERMI, HESS, AGIS and IceCube/DeepCore. We show that these models may be discovered in the near future. Specifically, measurements of diffuse gamma rays by FERMI can detect the start of a hard photon feature. We argue that these hard spectra can be produced by decaying dark matter and be consistent with current constraints, but are difficult to reconcile with models of annihilating DM. Consequently the measurement of a hard spectral feature, in correlation with the current cosmic ray measurements, will strongly favor decaying DM models. Finally we comment on the preliminary results from the Inner Galaxy presented by the FERMI collaboration.