The effect of the Fluorescence Yield selection on the energy scales of Auger, HiRes and TA

TL;DR

This paper examines how differences in fluorescence yield data and telescope optical efficiencies influence the energy scale calibration in cosmic ray experiments like Auger, HiRes, and TA, revealing significant deviations between some experiments.

Contribution

It provides an analytical method to evaluate the combined effects of fluorescence yield and optical efficiency on energy scale differences among major cosmic ray observatories.

Findings

Significant energy scale deviation between TA and Auger due to fluorescence yield differences.

No relevant energy scale difference between HiRes and Auger.

A simple analytical procedure can be applied to real data for calibration assessment.

Abstract

The fluorescence yield data used for shower reconstruction in the Auger, HiRes and TA experiments are different, not only in the overall absolute value but also in the wavelength spectrum and the various atmospheric dependencies. The effect on the energy reconstruction of using different fluorescence yield parameterizations is discussed. In addition, the impact of a change in the fluorescence spectrum depends on the optical efficiency of the telescopes. A simple analytical procedure allows us to evaluate the combined effect of fluorescence yield and optical efficiency showing a non-negligible deviation between the energy scales of TA and Auger. However no relevant effect is found in the comparison between HiRes and Auger. Finally we show that a similar procedure could also be applied with real data.