Longitudinal profile of extensive air showers

Air fluorescence experiment directly observes the nitrogen fluorescence light of air shower cascades in the Earth’s atmosphere and is therefore a unique tool to directly study the development of air showers and compare it to various models. In this paper, we fit the longitudinal profile and compare the quality of fit for a Gaussian function in shower age to the well known Gaisser–Hillas function and discuss how to average shower profiles in terms of age for alignment. To determine the χ2 for profile fitting in the simulation, effects caused by the use of the thinning algorithm have to be taken into account.