Constraints on evaporating primordial black holes from the AMS-02 positron data

Cosmic-ray (CR) positrons are relatively rare due to its secondary origin and thus sensitive to exotic contributions. Primordial black holes (PBHs) with masses above ~ 5×10¹⁴\,g can be stable sources of CR positrons due to Hawking radiation. We show that the CR positron flux measured by AMS-02 can place stringent constraints on the energy fraction of PBHs relative to that of dark matter fPBH. Making use of the state-of-the-art models for CR propagation in both the Galaxy and heliosphere, we obtain conservative upper limit of fPBH3× 10⁻⁴ at MPBH2× 10¹⁶ g, which improves the previous constraints obtained from the Voyager CR all-electron data by around an order of magnitude.