Calibration and Performance of the Surface Scintillator Detector of the Pierre Auger Observatory

TL;DR

This paper discusses the calibration methods and performance evaluation of surface scintillator detectors added to the Pierre Auger Observatory to improve cosmic-ray composition analysis.

Contribution

It introduces calibration techniques using muon peak and charge distributions and presents performance results of the upgraded surface scintillator detectors.

Findings

Successful calibration of SSDs using muon data

Stable detector performance over time

Enhanced cosmic-ray composition reconstruction

Abstract

The Pierre Auger Observatory has led to significant advances in our understanding of ultra-high-energy cosmic rays. These new insights have driven a major upgrade of the Observatory, known as AugerPrime, through which the experiment has entered its Phase II, a new period of data collection. A key part of the upgrade is adding surface scintillator detectors (SSD) on top of the existing water-Cherenkov detectors (WCD). The main goal is to leverage their different responses to the electromagnetic and muonic shower components, enhancing the reconstruction of the primary cosmic-ray mass. In this contribution, we present the methods that involve analyzing peak and charge distributions of atmospheric muons for accurate calibration during extensive air-shower event reconstruction, along with the development of a rate-based algorithm for independent calibration. We also show the performance of the SSDs with Phase-II data, including PMT reliability and stability of key parameters, such as gain and signal-to-noise ratio.