Spectral Signatures of PeVatrons

We analyze the energy distributions of final (stable) products—gamma rays, neutrinos, and electrons—produced in inelastic proton–proton collisions in the PeV energy regime. We also calculate the energy spectrum of synchrotron radiation from secondary electrons, assuming that these are promptly cooled in the surrounding magnetic field. We show that the synchrotron radiation has an energy distribution much shallower than that of primary protons, hence we suggest taking advantage of such a feature in the spectral analysis of the highest-energy (cutoff) emission region from particle accelerators. For a broad range of energy distributions in the parent protons, we propose simple analytical presentations for the spectra of secondaries in the cutoff region. These results can be used in the interpretation of high-energy radiation from PeVatrons—cosmic-ray factories accelerating protons to energies up to 1 PeV.