Determination of the invisible energy of extensive air showers from the data collected at Pierre Auger Observatory

Analisa G Mariazzi,Analisa G Mariazzi,For The Pierre Auger Collaboration

doi:10.1051/epjconf/201921002010

Abstract

In order to get the primary energy of cosmic rays from their extensive air showers using the fluorescence detection technique, the invisible energy should be added to the measured calorimetric energy. The invisible energy is the energy carried away by particles that do not deposit all their energy in the atmosphere. It has traditionally been calculated using Monte Carlo simulations that are dependent on the assumed primary particle mass and on model predictions for neutrino and muon production. In this work the invisible energy is obtained directly from events detected by the Pierre Auger Observatory. The method applied is based on the correlation of the measurements of the muon number at the ground with the invisible energy of the showers. By using it, the systematic uncertainties related to the unknown mass composition and to the high energy hadronic interaction models are significantly reduced, improving in this way the estimation of the energy scale of the Observatory.

Highlights

1015 eV cosmic rays are detected indirectly through the extensive air showers (EAS) they produce in the atmosphere
The reconstruction of inclined events [6] is based on the fact that the muon number distribution at ground level can be described by a density scaling factor that depends on E0 and primary mass, and by a lateral shape that, for a given arrival direction (θ, φ) of the shower, is consistently reproduced by different hadronic interaction models and depends only weakly on E0 and primary mass
A data driven estimation of Einv of cosmic ray showers detected by the Pierre Auger Observatory, was presented

Summary

Introduction

1015 eV cosmic rays are detected indirectly through the extensive air showers (EAS) they produce in the atmosphere. Most of the cosmic ray energy is carried by electromagnetic particles of the EAS, which can be detected by their secondary electromagnetic signatures, e.g. radio, Cherenkov or fluorescence light. An estimation of the primary energy E0 with the fluorescence detection technique is obtained by adding to Ecal a correction to account for the invisible energy (Einv) carried by the particles that do not dissipate all their energy in the atmosphere. The strategy followed in this work is to estimate Einv using the correlations that exist between Einv and shower observables measured at the Pierre Auger Observatory [4], correlations that to a large extent are not sensitive to the hadronic interaction models and primary mass composition. The FD operates during clear and moonless nights with a duty cycle of about 14% [5]

Phenomenology of the invisible energy

Estimation of Einv using Auger data

Einvrom inclined showers

Parameterisation of Einv as a function of Ecal

Findings

Conclusions