Speaker
Description
For more than 20 years, the Compton telescope (COMPTEL) had provided the best measurments of the Galactic diffuse MeV spectrum. Recently, our analysis of 16 years of data from the SPectrometer on INTEGRAL (SPI) [Siegert et. al (2022)] measured this emission with a higher signal-to-noise ratio. At MeV energies, the dominant contribution to the diffuse emission comes from inverse Compton scattering of low energy photons by cosmic-ray electrons. Nonetheless, sub-dominant emission from Primordial Black Hole (PBH) Dark Matter (DM) can be searched for in these data. Hypothetically formed from the collapse of overdensities before Big Bang nucleosynthesis, PBHs are interesting candidates for DM in the $\Lambda$CDM model of cosmology. PBHs of masses between $10^{16}$ and $10^{16}$ g, in the so-called asteroid mass range, are currently unconstrained and can saturate the DM cosmological abundance. MeV emission from PBH in this mass range is expected to come from PBH evaporation, a mechanism predicted by Stephen Hawking. In this talk, I will present our search for the PBH signal with 16 years of SPI data, and demonstrate that PBHs cannot account for all the DM if their mass is smaller than $4\times10^{17}$ g.
