Detection of primary photons in high energy cosmic rays using Cherenkov imaging and surface detectors

Discovered by Hess during some experiments about air ionization, cosmic rays are constituted by particles coming from the space. In the past, cosmic rays allowed the development of Particle Physics; indeed, thanks to their high energy not achievable in laboratories, they enabled new particles discovery. Today, interest about this radiation concerns both Astrophysics and Particle Physics. Indeed on the one hand, their knowledge allows formulation about new models of Universe structure and evolution or to acquire new knowledge about final objects of stars evolution; on the other hand cosmic rays allows us to study fundamental processes, as for example acceleration and interaction mechanisms of particles at energies not achievable in laboratories. Although it has passed more than a century after their discovery, there are many questions to which it isn’t possible to answer yet or to which there isn’t certainty about formulated theories. Some examples are about objects that can accelerate particles to high energy and acceleration mechanisms; indeed, even if there are some theories, we don’t have experimental certainty. Moreover, although measured in many experiments, energy spectrum shows, especially in the region called "Knee", some differences between measuring made by experiments. Since magnetic fields deflect charged particles, their observation doesn’t allow to go back to the source, so in cosmic rays study it’s very important γ rays observation because they aren’t deflected by magnetic fields. In 1989 Whipple experiment allowed to observe, for the first time, TeV energy γ rays coming from Crab Nebula. Thanks to many experiments made to answer questions about cosmic rays, more than 100 Very High Energy (VHE) γ rays sources were observed since then; 60 out of 100 have galactic origin, as for instance Supernova Remnants or Pulsars; for the rest, apart from those not identified, they have extra-galactic origin. In this work some simulations, made by National Nuclear Physics Institute (INFN) subdivision of Torino (Italy) using Cosmic Ray SImulations for KAscade (CORSIKA), were analyzed to study differences between Extensive Air Shower (EAS) produced by γ rays and EAS produced by protons.