Sensitivity of cosmic-ray experiments to ultra-high-energy photons: reconstruction of the spectrum and limits on the superheavy dark matter

Understand

We estimate the sensitivity of various experiments detecting ultra-high-energy cosmic rays to primary photons with energies above 10^19 eV.

• We demonstrate that the energy of a primary photon may be significantly (up to a factor of ~ 10) under- or overestimated for particular primary energies and arrival directions.
• We consider distortion of the reconstructed cosmic-ray spectrum for the photonic component.
• As an example, we use these results to constrain the parameter space of models of superheavy dark matter by means of both the observed spectra and available limits on the photon content.