Constraining dark matter using 20-year INTEGRAL/IBIS observations I: Primordial black holes

Abstract

Primordial black holes (PBHs) in the asteroid-mass window remain a viable dark matter candidate. In the lower part of this mass range, Hawking evaporation produces electrons and positrons that generate diffuse hard X-ray emission through inverse Compton (IC) scattering on Galactic radiation fields. We present the first search for this signal using a combined spectral and morphological analysis of the 20-year INTEGRAL/IBIS observations. We construct a physically motivated model of the Galactic hard X-ray background, including IC emission from cosmic-ray electrons and unresolved accreting white dwarfs, and consistently incorporate the IC contribution from PBH evaporation. By exploiting both spatial and spectral information, we improve the separation between a possible PBH signal and astrophysical backgrounds compared to analyses based only on spectral data. We derive constraints on the PBH dark matter fraction over a broad mass range, including extended PBH mass functions and rotating PBHs. We assess the impact of uncertainties in cosmic-ray propagation and the Galactic dark matter density profile, finding that the propagation of low-energy electrons and positrons represents the main source of uncertainty in the predicted signal. Despite these limitations, our results provide competitive constraints over a wide range of PBH masses, highlighting the potential of hard X-ray observations as a complementary probe of evaporating PBHs.