Exploring memory-burdened primordial black holes with ultrahigh-energy cosmic-rays

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Abstract
Quantum backreaction effects may quench Hawking evaporation through a “memory burden,” allowing primordial black holes (PBHs) with formation masses well below 10 15 g to survive to the present and contribute to the dark matter. We show that ultrahigh-energy cosmic rays (UHECRs) provide a powerful and previously unexplored probe of this scenario. We compute the proton and neutron emission from memory-burdened PBHs, including the Galactic-halo contribution and the extragalactic proton component, and confront it with the Pierre Auger Observatory proton spectrum and its EeV neutron limits from the Galactic plane. This yields new constraints on the PBH dark-matter fraction as a function of the PBH formation mass and the evaporation-suppression parameter k . For k ≳ 3 the nonobservation of ultrahigh-energy protons leads to bounds competitive with those from UHE gamma rays, while neutron limits remain comparable to high-energy neutrino constraints. Our results highlights the key role of multimessenger astronomy in constraining beyond-the-standard-model scenarios.
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Funding Information
  • European Commission
  • NextGenerationEU (PRIN-MUR 2022TJW4EJ)
  • Ministero dell'Università e della Ricerca (ECS00000041—VITALITY/ASTRA)
  • Ministero dell'Università e della Ricerca (CUP D13C21000430001)
  • Istituto Nazionale di Fisica Nucleare Sezione di Padova
  • NUSES (CUP: D12F19000040003)

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