Title: Search for electromagnetic super-preshowers using gamma-ray telescopes,
Abstract: Any considerations on propagation of particles through the Universe must
involve particle interactions: processes leading to production of particle
cascades. While one expects existence of such cascades, the state of the art
cosmic-ray research is oriented purely on a detection of single particles,
gamma rays or associated extensive air showers. The natural extension of the
cosmic-ray research with the studies on ensembles of particles and air showers
is being proposed by the CREDO Collaboration. Within the CREDO strategy the
focus is put on generalized super-preshowers (SPS): spatially and/or temporally
extended cascades of particles originated above the Earth atmosphere, possibly
even at astrophysical distances. With CREDO we want to find out whether SPS can
be at least partially observed by a network of terrestrial and/or satellite
detectors receiving primary or secondary cosmic-ray signal. This paper
addresses electromagnetic SPS, e.g. initiated by VHE photons interacting with
the cosmic microwave background, and the SPS signatures that can be seen by
gamma-ray telescopes, exploring the exampleof Cherenkov Telescope Array. The
energy spectrum of secondary electrons and photons in an electromagnetic
super-preshower might be extended over awide range of energy, down to TeV or
even lower, as it is evident from the simulation results. This means that
electromagnetic showers induced by such particles in the Earth atmosphere could
be observed by imaging atmospheric Cherenkov telescopes. We present preliminary
results from the study of response of the Cherenkov Telescope Array to SPS
events, including the analysis of the simulated shower images on the camera
focal plane and implementedgeneric reconstruction chains based on the Hillas
parameters.