Indirect Dark Matter Searches in the Light of the Recent Ams-02 Observations

Abstract

Abstract. If the astronomical dark matter is made of weakly interacting, massive and stable species, it should annihilate on itself into particles. This process should produce rare antimatter cosmic rays and lead to distortions in their energy distributions. The AMS-02 spectrometer has been measuring them with unprecedented accuracy. It is timely to investigate if anomalies have been found in the positron and antiproton spectra and if so, if they indirectly point toward the presence of DM particles annihilating inside the Milky Way.1 Cosmic rays as an indirect probe for dark matterThe universe contains a substantial fraction of its mass under the form of the so-called astronomical dark matter (DM), a pressureless component found inside galaxies [1,2], clusters of galaxies [3] and on cosmological scales. The recent observations of the Planck satellite [4] have confirmed the picture of a flat universe filled with dark energy (68.3%), dark matter (26.8%) and baryons (4.9%). According to this standard lore, the astronomical dark matter cannot be made of baryons and its nature is still unknown. Many solutions have been proposed for the last three decades. Among the numerous possibilities, a particular candidate under the form of a weakly interacting massive particle dubbed WIMP has attracted much attention. This species is naturally present in most extensions of the standard model of particle physics. It is stable by conservation of a quantum number, such as R-parity in supersymmetry or the momentum along the extra-dimensions in Kaluza-Klein inspired models. It interacts with its surroundings and annihilates on itself through typically weak interactions. The crucial consequence, that makes WIMPs so interesting, is that they are produced during the Big Bang with a relic abundance close to the Planck value of Ω DM h 2 = 0.1196 ± 0.0031. For this to happen, the annihilation cross section σv should be close to the canonical value of 3 × 10 −26 cm 3 s −1 . The searches for WIMP-like DM have developed along three directions. First, WIMPs could be produced at colliders such as the LHC and appear in missing energy events. An abnormally large rate of gluon monojets or single gauge boson events could be explained by the fusion of quark-antiquark pairs into pairs of DM particles. A second line of research, called direct detection, is based on the potential collisions of WIMPs on a terrestrial instrument. As an impinging a