Near future MeV telescopes can discover asteroid-mass primordial black hole dark matter

TL;DR

Upcoming MeV gamma-ray telescopes like AMEGO could significantly improve constraints on asteroid-mass primordial black holes as dark matter candidates by detecting their Hawking radiation signatures.

Contribution

This work forecasts the detection capabilities of future MeV telescopes for asteroid-mass PBHs, extending current bounds and considering rotating and extended mass distributions.

Findings

AMEGO-like telescopes can exclude non-rotating PBHs up to 7×10^{17} g as sole dark matter component.

Forecasted constraints surpass current bounds by nearly an order of magnitude.

Constraints are more stringent for rotating PBHs and those with extended mass distributions.

Abstract

Primordial black holes (PBHs), formed out of large overdensities in the early Universe, are a viable dark matter (DM) candidate over a broad range of masses. Ultra-light, asteroid-mass PBHs with masses around $10^{17}$ g are particularly interesting as current observations allow them to constitute the entire DM density. PBHs in this mass range emit $\sim$ MeV photons via Hawking radiation which can directly be detected by the gamma ray telescopes, such as the upcoming AMEGO. In this work we forecast how well an instrument with the sensitivity of AMEGO will be able to detect, or rule out, PBHs as a DM candidate, by searching for their evaporating signature when marginalizing over the Galactic and extra-Galactic gamma-ray backgrounds. We find that an instrument with the sensitivity of AMEGO could exclude non-rotating PBHs as the only DM component for masses up to $7 \times 10^{17}$ g at 95% confidence level (C.L.) for a monochromatic mass distribution, improving upon current bounds by nearly an order of magnitude. The forecasted constraints are more stringent for PBHs that have rotation, or which follow extended mass distributions.