Ultrahigh Energy Cosmic Rays Detection

The paper describes methods used for the detection of cosmic rays with energies above 1018 eV (UHECR, UltraHigh Energy Cosmic Rays). It had been anticipated there would be a cutoff in the energy spectrum of primary cosmic rays around 3⋅1019 eV induced by their interaction with the 2.7 °K primordial photons. This has become known as the GZK cutoff. However, several showers have been detected with estimated primary energy exceeding this limit.