  Light, asteroid-mass primordial black holes, with lifetimes in the range
between hundreds to several millions times the age of the universe, are
well-motivated candidates for the cosmological dark matter. Using archival
COMPTEL data, we improve over current constraints on the allowed parameter
space of primordial black holes as dark matter by studying their evaporation to
soft gamma-rays in nearby astrophysical structures. We point out that a new
generation of proposed MeV gamma-ray telescopes will offer the unique
opportunity to directly detect Hawking evaporation from observations of nearby
dark matter dense regions and to constrain, or discover, the primordial black
hole dark matter.
