Event reconstruction with the Radio detector of the Pierre Auger Observatory

TL;DR

This paper describes the methods and recent developments in reconstructing extensive air showers using the radio detector of the Pierre Auger Observatory, emphasizing calibration, detector characterization, and accurate parameter estimation.

Contribution

It presents a comprehensive reconstruction pipeline for radio-detected air showers, including calibration, detector characterization, and precise estimation of shower parameters.

Findings

Shower arrival direction can be determined within 0.2 degrees.

Electromagnetic cascade energy can be estimated within 5%.

Absolute calibration achieved at 5% accuracy.

Abstract

The surface detector of the Pierre Auger Observatory has recently been upgraded with the addition of radio antennas, forming the radio detector (RD). This contribution outlines the standard methods for reconstructing extensive air showers using the RD, along with recent developments. The reconstruction pipeline is based on a robust understanding of the detector itself. The entire instrument, including the antenna pattern and analog chain, has been meticulously characterized within the Offline software framework, based on measurements in the laboratory as well as in the field. To ensure data integrity, stations identified as unreliable through monitoring are excluded before event reconstruction. Absolute calibration is achieved at the 5 percent level by analyzing the diffuse galactic radio emission. Next, the electric field that induced voltages in the antenna is calculated by unfolding the antenna response pattern. Key observables, such as the energy fluence (the energy deposited in the ground per unit area) and the arrival time of the pulse, are then determined. With these quantities, shower parameters can be reconstructed with very good accuracy in two chi-square-minimization fits: one to determine the shower's arrival direction via a spherical wavefront fit (predicted within 0.2 degree), and the other to estimate the distance to the shower maximum and the electromagnetic cascade energy (predicted within 5 percent) using a lateral density function