Observation of electron rings with imaging air Cherenkov telescopes
2019 July 22
The detection of muons in cosmic air showers with imaging air Cherenkov telescopes is an established method for the calibration of the detection efficiency of Cherenkov light of the entire optical system. Similar to muons, electrons passing the observation level near the telescope produce ring-like images. Images from electron rings can be potentially used to measure the electron energy and its energy-loss through ionization and Bremsstrahlung in the atmosphere. We use both, CORSIKA simulations as well as analytical calculations, to predict the shape of electron rings and the number of visible photons generated by electrons in the air shower. We investigate the opportunity to register electron rings with the current imaging air Cherenkov telescopes. It can be expected that the electron ring images are distinctly different from muon generated rings: since electrons below the critical energy continuously lose energy through ionization and suffer multiple elastic scattering, the rings are less sharp than the muon-induced rings. Our future plans will be to check the visibility of rings with the current and next generation imaging Cherenkov telescopes (e.g. HESS Phase II, MAGIC, TAIGA, CTA) by calculating an estimate for the rate of observable rings and the relevant energy range of cosmic-rays. Furthermore we will perform a search for electron rings in data from observations with low altitude cloud coverage. Finally, we will consider the possibilities to reconstruct the energy of electrons in the air shower using the observed electron rings.