Constraining primordial black hole masses with the isotropic gamma ray background

Primordial black holes (PBHs) can represent all or most of the dark matter in the window 1017–1022 g. Here we present an extension of the constraints on PBHs of masses 1013–1018 g arising from the isotropic diffuse gamma-ray background. Primordial black holes evaporate by emitting Hawking radiation that should not exceed the observed background. Generalizing from monochromatic distributions of Schwarzschild black holes to extended mass functions of Kerr rotating black holes, we show that the lower part of this mass window can be closed for near-extremal black holes.