Speaker
Description
Determining the absolute energy scale in cosmic-ray observations is both challenging and of fundamental importance. We show that radio measurements of extensive air showers with the Auger Engineering Radio Array, combined with per-event CoREAS simulations, enable an accurate calibration of the cosmic-ray energy scale between 3 x $10^{17}$ eV and several $10^{18}$ eV. To ensure an accurate result, we control individual systematic uncertainties at the 5% level or better. The absolute calibration of the antenna gain and the analog signal chain is performed using the Galactic background emission and detailed antenna gain modeling, cross-checked with laboratory measurements. Further key elements include temperature-dependent amplification corrections, continuous detector monitoring, thunderstorm vetoing, unbiased event reconstruction, and per-event atmospheric modeling. The resulting AERA energy scale is 12% higher than the one established with the Auger Fluorescence Detector, consistent within uncertainties and providing an independent confirmation of the absolute energy scale of the Pierre Auger Observatory.