Comparison of available measurements of the absolute fluorescence yield

TL;DR

This paper compares various measurements of the absolute fluorescence yield at 337 nm, normalizing them to a common basis, and discusses corrections based on detailed Monte Carlo simulations to improve energy reconstruction accuracy in air shower experiments.

Contribution

It provides a standardized comparison of fluorescence yield measurements and proposes corrections based on detailed energy deposition simulations.

Findings

Normalized fluorescence yields at 337 nm for different experiments.

Identified discrepancies and proposed correction factors.

Enhanced accuracy in fluorescence yield values for air shower analysis.

Abstract

The uncertainty in the absolute value of the fluorescence yield is still one of the main contributions to the total error in the reconstruction of the primary energy of ultra-energetic air showers using the fluorescence technique. A significant number of experimental values of the fluorescence yield have been published in the last years, however reported results are given very often in different units (photons/MeV or photons/m) and for different wavelength intervals. In this work we present a comparison of available results normalized to its value in photons/MeV for the 337 nm band at 800 hPa and 293 K. The conversion of photons/m to photons/MeV requires an accurate determination of the energy deposited by the electrons in the field of view of the experimental setup. We have calculated the energy deposition for each experiment by means of a detailed Monte Carlo simulation including when possible the geometrical details of the particular setup. Our predictions on deposited energy, as well as on some geometrical factors, have been compared with those reported by the authors of the corresponding experiments and possible corrections to the fluorescence yields are proposed.