In most cosmological models, primordial black holes (PBHs) should have formed
in the early Universe. Their Hawking evaporation into particles could
eventually lead to the formation of antideuterium nuclei. This paper is devoted
to a first computation of this antideuteron flux. The production of these
antinuclei is studied with a simple coalescence scheme, and their propagation
in the Galaxy is treated with a well-constrained diffusion model. We compare
the resulting primary flux to the secondary background, due to the spallation
of protons on the interstellar matter. Antideuterons are shown to be a very
sensitive probe for primordial black holes in our Galaxy. The next generation
of experiments should allow investigators to significantly improve the current
upper limit, nor even provide the first evidence of the existence of
evaporating black holes.Comment: Final version, published in Astronomy & Astrophysic