A complete model of the signal in surface detector arrays and its application for the reconstruction of mass-sensitive observables

The principle of Air Shower Universality yields a method of understanding Extensive Air Showers of UHECRs as a superposition of different particle components whose spatial and temporal distributions follow individual analytical profile functions. We present a model of the expected densities of particles in time and space that uses the depth of the shower maximum, Xmax, and the relative muonic content of the shower, Rμ, as input parameters. The model is fine-tuned and tested with simulated showers using different hadronic interaction models. Furthermore, we present results for the reconstruction of Xmax and Rμ that allow for an event-by-event estimation of the mass of the primary particle, based on the responses of the water-Cherenkov and scintillator surface detectors of the Auger Observatory.