Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 20: Cosmic Rays I

T 20.1: Talk

Monday, March 16, 2026, 16:15–16:30, KS 00.006

The Roving Laser System for Absolute Energy Calibration of the Fluorescence Telescopes at the Pierre Auger Observatory^* — •Rukije Uzeiroska-Geyik for the Pierre Auger collaboration — Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal

The Fluorescence Detector (FD) of the Pierre Auger Observatory provides energy measurements of primary cosmic rays that are largely independent of specific interaction models. The FD energy measurement is crucial for calibrating the energy reconstruction of the Surface Detector. Consequently, the accuracy of the FD energy calibration plays a significant role in the systematic uncertainties associated with nearly all scientific results of the Observatory. To this end, a laser with a well-defined energy output will be fired in the field of view of the FD telescopes. Unlike other calibration methods, the response of the telescopes to the laser closely simulates its reaction to an actual cosmic-ray air shower. The system was designed with special attention to the depolarization of the laser beam to ensure a consistent relationship between energy output and directional light yield.

This contribution presents the results of the laboratory test measurements of the laser system, which were performed to validate and optimize its performance before field deployment. In addition, we report on the preparations for the first in-field calibration campaign of the FD telescopes in Argentina.

Keywords: Fluorescence Light; Fluorescence Detector; Energy Calibration; Roving Laser System