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

A. MARIAZZI; THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

Simposio; International Symposium on Ultra High Energy Cosmic Rays UHECR 2018; 2018

In order to get the primary energy of cosmic rays from their extensive air showers using the fluorescencedetection technique, the invisible energy should be added to the measured calorimetric energy. Theinvisible 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 primaryparticle 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 withthe invisible energy of the showers. By using it, the systematic uncertainties related to the unknown masscomposition and to the high energy hadronic interaction models are significantly reduced, improving in thisway the estimation of the energy scale of the Observatory.