Monte Carlo studies of geomagnetic field effects on the imaging air Cherenkov technique for the MAGIC telescope site

Imaging air Cherenkov telescopes (IACTs) detect the Cherenkov light from extensive air showers (EAS) initiated by very high energy (VHE) γ -rays impinging on the Earthʹs atmosphere. Due to the overwhelming background from hadron-induced EAS, the discrimination of the rare γ -like events is vital. The influence of the geomagnetic field (GF) on the development of EAS can further complicate the imaging air Cherenkov technique. The amount and the angular distribution of Cherenkov light from EAS can be obtained by means of Monte Carlo (MC) simulations. Here we present the results from dedicated MC studies of GF effects on images from γ -ray initiated EAS for the MAGIC telescope site, where the GF strength is ∼ 40 μ T . The results from the MC studies suggest that GF effects degrade not only measurements of very low energy γ -rays below ∼ 100 GeV but also those at TeV-energies.