A comprehensive study of shower to shower fluctuations

TL;DR

This paper uses Monte Carlo simulations to analyze the different sources of shower to shower fluctuations in extensive air showers, including physical and artificial fluctuations caused by thinning procedures, providing methods to estimate true fluctuations.

Contribution

It introduces a detailed analysis of shower fluctuations, distinguishing physical from artificial effects, and offers expressions to estimate true fluctuations despite thinning-induced noise.

Findings

Thinning levels above 10^(-5) significantly affect fluctuation measurements.

Artificial fluctuations from thinning can be mitigated with proposed estimation methods.

Fluctuations in the depth of first interaction also impact overall shower variability.

Abstract

By means of Monte Carlo simulations of extensive air showers (EAS), we have performed a comprehensive study of the shower to shower fluctuations affecting the longitudinal and lateral development of EAS. We split the fluctuations into physical fluctuations and those induced by the thinning procedure customarily applied to simulate showers at EeV energies and above. We study the influence of thinning on the calculation of the shower to shower fluctuations in the simulations. For thinning levels larger than 10^(-5) - 10^(-6), the determination of the shower to shower fluctuations is hampered by the artificial fluctuations induced by the thinning procedure. However, we show that shower to shower fluctuations can still be approximately estimated, and we provide expressions to calculate them. The influence of fluctuations of the depth of first interaction on the determination of shower to shower fluctuations is also addressed.