Hybrid approach to the primary cosmic ray composition

Abstract : Direct Cherenkov light emitted by primary cosmic ray particles prior to their first interaction in the atmosphere has been detected by the H.E.S.S. Imaging Atmospheric Cherenkov Telescopes. Thus, an energy spectrum for iron nuclei in the energy range 50-200 TeV has been derived. This paper discusses the advantage of combining this novel technique with a classic extensive air shower array in order to test the different criteria used for the identification of primary cosmic ray particles (muon and electron abundances, hadron content and lateral profiles). Such a hybrid experiment will offer a unique opportunity to approach the elemental composition around the knee of the primary cosmic ray energy spectrum when validated criteria are extended beyond the present direct Cherenkov energy window.