Energy estimation of cosmic rays with the Engineering Radio Array of the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION, INCLUYE S. MOLLERACH

PHYSICAL REVIEW D - PARTICLE AND FILDS

American Physical Society

Año: 2016

0556-2821

The Auger Engineering Radio Array (AERA) is part of the Pierre AugerObservatory and is used to detect the radio emission of cosmic-ray airshowers. These observations are compared to the data of the surfacedetector stations of the Observatory, which provide well-calibratedinformation on the cosmic-ray energies and arrival directions. Theresponse of the radio stations in the 30-80 MHz regime has beenthoroughly calibrated to enable the reconstruction of the incomingelectric field. For the latter, the energy deposit per area isdetermined from the radio pulses at each observer position and isinterpolated using a two-dimensional function that takes into accountsignal asymmetries due to interference between the geomagnetic andcharge-excess emission components. The spatial integral over the signaldistribution gives a direct measurement of the energy transferred fromthe primary cosmic ray into radio emission in the AERA frequency range.We measure 15.8 MeV of radiation energy for a 1 EeV air shower arrivingperpendicularly to the geomagnetic field. This radiationenergy?corrected for geometrical effects?is used as acosmic-ray energy estimator. Performing an absolute energy calibrationagainst the surface-detector information, we observe that thisradio-energy estimator scales quadratically with the cosmic-ray energyas expected for coherent emission. We find an energy resolution of theradio reconstruction of 22% for the data set and 17% for a high-qualitysubset containing only events with at least five radio stations withsignal.