Indirect detection of decaying dark matter

Present evidence for dark matter in our Galaxy and in the Universe at large does not exclude the possibility that the dark matter particles could be unstable. If this is the case, their decays into positrons, antiprotons or gamma rays might occur at rate sufficiently large to allow indirect dark matter detection through an anomalous contribution to the high-energy cosmic-ray fluxes. In this work, we show that the positron excess observed by the PAMELA collaboration could be explained by the decay of dark matter particles, provided they have a mass larger than ̃ 300 GeV, a lifetime around 10 ²⁶s, and decay preferentially into hard leptons of the first or second generation. We also discuss the constraints on the properties of the dark matter particles which stem from the non-observation of an exotic contribution in the antiproton flux. Finally, we estimate the contributions to the diffuse gamma-ray background from dark matter decay, which will be tested in the near future by the Fermi Large Area Telescope.