Abstract
The study of anomalous longitudinal profiles of extensive air showers presents an interesting opportunity to gain additional insight about the character of hadronic interactions at the highest energies. Moreover, the presence of such profiles would represent direct evidence of a light component in the primary cosmic rays of a given energy, independently of hadronic interaction models. The ratio of profiles observed to have a “double bump” structure (with two clearly distinguishable atmospheric depths of maximum particle count) compared to the total number of events can moreover be used to test the predictions of interaction models. However, the majority of such profiles observed at the Pierre Auger Observatory are caused by clouds. Here we describe a method of rapid monitoring of particularly interesting cosmic ray events, using the F/Photometric Rapid Atmospheric Monitor (FRAM) telescope to identify events with clear, cloudless atmospheric background. The function of FRAM is described in detail and the number of triggered events is presented.
Highlights
The longitudinal profiles are generally very well described by the so called Gaisser-Hillas (G.-H.) function [5], an empirical Ansatz of the form Xmax −X0 NGH(X) = NmaxX − X0 Xmax − X0 λ exp Xmax − X λ, where X is the atmospheric slant depth, NGH the number of particles at that given depth, Nmax the number of particles at the shower maximum depth Xmax and the remaining X0 and λ are energy-dependent fit parameters without a consistent physical interpretation
The ratio of profiles observed to have a “double bump” structure compared to the total number of events can be used to test the predictions of interaction models
The majority of such profiles observed at the Pierre Auger Observatory are caused by clouds
Summary
The longitudinal profiles are generally very well described by the so called Gaisser-Hillas (G.-H.) function [5], an empirical Ansatz of the form. A similar phenomenon can occur during the development of a single shower, when a (leading) particle leaves the evolving cascade early during shower development and manages to propagate deeply into the atmosphere Such a particle forms a secondary sub-shower, which, if it possesses a significant fraction of the energy of the primary particle, is clearly discernible from the primary sub-shower. The rate of occurrence of anomalous showers can be examined by looking at the properties of a statistically large sample of simulated longitudinal profiles For this kind of study, where the lateral features and the distribution of particles at the ground are of no interest, the CONEX [6] software presents an ideal tool. The FRAM telescope (described below in the text) does not have information about this particular event
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