Identification of cosmic ray primaries using the longitudinal muon profile of EAS

  Moon Moon Devi  ,  Ran Budnik   
Weizmann Institute of Science

The measurement of the individual charged particles in an Extensive Air Shower (EAS), at a surface detector array, would provide important distinguishing parameters to identify the cosmic primary particle. These will also contribute to the mapping of the very high energy interactions in the topmost layers of the atmosphere, i.e., beyond the reach of current accelerators, and to probe anomalies beyond QCD. The direct detectors placed in balloons or satellites and can probe the composition of cosmic primaries with energy up to about 1014.5 eV only. The ongoing attempts to study individual muons are limited in their expandability to larger arrays. New developments in detector technology allow for a realistic cost of large area detectors, however with limitations on energy resolutions, directional information and dynamic range. In this study, we perform a simulation study using CORSIKA to combine the longitudinal profile of the muons, characterized by their energy spectrum and lateral spread, with the depth at shower maximum (Xmax) of an EAS initiated by a primary at ultra high energies (1016 eV - 1019 eV). Firstly, using proton and iron as the shower primaries, we show that the muon observables and Xmax together can be used to identify the primary. This study is then generalized with three groups of primaries, light (Z ≤ 2), medium (3 ≤ Z  ≤ 11) and heavy (12  ≤ Z  ≤ 26). This study can be used to design a future detector for surface array, which will be able to enhance our knowledge of primaries and UHE interactions.