Reconstruction of inclined air showers detected with the Pierre Auger Observatory

TL;DR

This paper presents a new method for reconstructing highly inclined cosmic-ray air showers detected by the Pierre Auger Observatory, enabling better energy spectrum measurements of ultra-high energy cosmic rays.

Contribution

It introduces a novel reconstruction technique for inclined air showers using muon density models, improving analysis of ultra-high energy cosmic rays.

Findings

Method accurately reconstructs inclined air showers.

Calibrated cosmic ray energy using hybrid detection techniques.

Enables independent measurement of cosmic ray energy spectrum.

Abstract

We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than $60^\circ$ detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.