The highest-energy cosmic rays measured with the Pierre Auger Observatory over the past decade provide us with unprecedented glimpses into their origin and properties. Improvements to this understanding will come from a major upgrade stage of the Observatory denominated AugerPrime. The upgrade program will include new plastic scintillator detectors on top of all water-Cherenkov detectors, faster and more powerful electronics, and the extension of the dynamic range.
Complementing the water-Cherenkov detectors of the surface array with scintillator detectors, we will be able to evaluate the muonic component of the showers better and thus to estimate the primary mass of the ultra high energy cosmic rays on an event by event basis, reaching the region of the flux suppression. The enhanced information on composition will allow us to perform anisotropy studies on selections of mass groups and to explore the hadronic interactions in an unexplored energy and kinematic region.
After introducing the physics motivation for upgrading the Auger Observatory, the planned detector upgrade and the technical realization will be presented, with an emphasis on the expected performance and the improved physics sensitivity.