Search for Extensive Photon Cascades with the Cosmic-Ray Extremely
  Distributed Observatory
  Although the photon structure is most efficiently studied with the
accelerator instruments, there is also a scientifically complementary potential
in investigations on photons produced in the outer space. This potential is
already being explored with gamma ray telescopes, ultra-high energy cosmic ray
observatories and, since very recently, by the Cosmic-Ray Extremely Distributed
Observatory (CREDO). Unlike the former instruments focused on detection of
single photons, CREDO aims at the detection of cascades (ensembles) of photons
originating even at astrophysical distances. If at least a part of such a
cascade reaches Earth, it might produce a unique pattern composed of a number
of air showers observable by an appropriately dense array of standard
detectors. If the energies of air showers constituting the pattern are
relatively low and if the typical distances between the neighbors are large,
the ensemble character of the whole phenomenon might remain uncovered, unless
the CREDO strategy is implemented.
