The energy scale of the Pierre Auger observatory

Abstract

The measurement of energy is one of the most important and challenging tasks of an astroparticle observatory, especially given that the energy must be accompanied by reliable statistical and systematic uncertainties. The energy scale of the Pierre Auger Observatory is based on observations made by its fluorescence detector, taking advantage of the near-calorimetric measurements afforded by this technique. This fluorescence energy calibration is transferred to the surface detector measurements via coincident fluorescence and surface detector observations of air showers at the hybrid observatory. In this contribution, we present the current status of our energy scale. We demonstrate our confidence in the cosmic ray energy assignments by discussing our methods and their systematic and statistical uncertainties. We describe the impact of recent improvements in the estimation of invisible energy, and discuss uncertainties associated with the fluorescence yield, the atmosphere, detector calibration, and the event reconstruction process.