Fundamental physics with cosmic Gamma Rays, and the CTA experiment
Alessandro De Angelis
(Universita` di Udine - IST. Lisboa)
Aula Seminari (LNF INFN)
Via Enrico Fermi, 40
Gamma-ray astrophysics studies electromagnetic radiation of cosmic origin in the energy range above some 30 MeV and up to some 100 TeV. Observations in this energy band are performed: from space, by the Large Area Telescope onboard the Fermi satellite and from the AGILE detector; from Earth, mostly by the Imaging Air Cherenkov Telescopes MAGIC, H.E.S.S. and VERITAS, and by the extensive air shower detector HAWC. These instruments have discovered in the recent years different populations of gamma-ray emitters and studied in detail the non-thermal astrophysical processes producing high-energy radiation, in particular in correlation with the acceleration of cosmic rays. The scientific objectives of gamma-ray astrophysics include also questions related to fundamental physics. By observing the gamma-ray emission from sources at cosmological distances, we learn about the spectral intensity and evolution of the intergalactic background radiation, and perform tests of Lorentz Invariance and of vacuum energy. Moreover, we search for dark matter by looking for possible signatures in final states involving gamma rays or positrons. A new detector, CTA, is in construction, and it will outperform by at least one order of magnitude the present gamma-ray detectors.