  Ultra-high energy photons constitute one of the most important pieces of the
astroparticle physics problems. Their observation may provide new insight on
several phenomena such as supermassive particle annihilation or the GZK effect.
Because of the absence of any significant photon identification by a leading
experiments such as the Pierre Auger Observatory, we consider a screening
phenomenon called preshower effect which could efficiently affect ultra-high
energy photon propagation. This effect is a consequence of photon interactions
with the geomagnetic field and results in large electromagnetic cascade of
particles several thousands kilometers above the atmosphere. This collection of
particles, called cosmic-ray ensembles (CRE), may reach the atmosphere and
produce the well-known air showers. In this paper we propose to use gamma-ray
telescopes to look for air showers induced by CRE. Possible sources of
ultra-high energy photons include the GZK effect and Super Heavy Dark Matter
particles. Simulations involving the preshower effect and detectors response
are performed and properties of these peculiar air showers are investigated.
The use of boosted decision trees to obtain the best cosmic-ray ensemble/hadron
separation, the aperture and event rate predictions for a few models of photon
production are also presented.

Instrumentation and Methods for Astrophysics