Late-forming black holes and the antiproton, gamma-ray, and anti-helium excesses

Abstract

Black holes long-lived enough to be the dark matter have temperatures below the MeV. Since Hawking evaporation is a quasi-thermal process, no GeV emission is predicted to be produced by black holes if they are part, or all, of the cosmological dark matter. However, black holes could be ``spawned'' at late times with masses that correspond to short lifetimes, and as such be significantly hotter and produce particles well in excess of the GeV. Here we investigate if such late-forming black holes could, at once, explain the tantalizing excesses found in the gamma radiation from the Galactic center, in the flux of cosmic-ray antiproton, and in the few tentative antihelium events reported by the anti-matter spectrometer AMS-02. We find that late-forming black holes cannot simultaneously explain all these excesses. We additionally compute accurate predictions for the anti-deuteron, high-energy neutrino, and positron fluxes if this scenario is realized in nature. We find that while the neutrino and positron fluxes are too small compared to the expected background, a significant number of anti-deuteron events is expected both at AMS-02 and at the future General AntiParticle Spectrometer (GAPS).