Indirect detection of unstable heavy dark matter

Abstract Unstable relics with lifetime longer than the age of the Universe could be the dark matter today. Electrons, photons and neutrinos are a natural outcome of their decay and could be searched for in cosmic rays and in γ-ray and neutrino detectors. I compare the sensitivities of these three types of searches to the mass and lifetime of a generic unstable particle. I show that if the relics constitute our galactic halo and their branching ratios into electron-positrons, photons and neutrinos are comparable, neutrino searches would probe the longest lifetimes for masses ≳ 40 TeV, while electron-positron searches would be better but more uncertain for lighter particles. If instead the relics are not clustered in our halo, neutrinos are more sensitive a probe than γ-rays for masses ≳ 700 GeV. A 1 km 2 neutrino telescope should be able to explore lifetimes up to ∼10 30 s while searching for neutrinos from unstable particles above the atmospheric background.