Refining Galactic primordial black hole evaporation constraints

Abstract

We revisit the role of primordial black holes (PBHs) as potential dark matter (DM) candidates, particularly focusing on light asteroid-mass PBHs. These PBHs are expected to emit particles through Hawking evaporation that can generate cosmic rays (CRs), eventually producing other secondary radiations through their propagation in the Milky Way, in addition to prompt emissions. Here, we perform a comprehensive analysis of CR signals resulting from PBH evaporation, incorporating the full CR transport to account for reacceleration and diffusion effects within the Milky Way. In particular, we revisit the e± flux produced by PBHs, using Voyager 1, and study for the first time the diffuse x-ray emission from the up-scattering of Galactic ambient photons due to PBH-produced e± via the inverse Compton effect using Xmm-Newton data, as well as the morphological information of the diffuse 511 keV line measured by Integral/Spi. In doing so, we provide leading constraints on the fraction of DM that can be in form of PBHs in a conservative way, while also testing how different assumptions on spin and mass distributions affect our conclusions.