On the possibility of primary identification of individual cosmic ray showers

Abstract

The transition between the Galactic and extragalactic cosmic ray components could take place either in the region of the spectrum known as the second knee or in the ankle. There are several models of the transition but it is not possible to confirm or even rule out any of them from the flux measurement alone. Therefore, the measurement of the composition as a function of primary energy will play a fundamental role for the understanding of this phenomenon.In this work we study the possibility of primary identification in an event by event basis in the ankle region, around E = 10 18 eV. We consider as case study the enhancements of the Pierre Auger Southern Observatory, which are under construction in Malagüe, Province of Mendoza, Argentina. We use a non-parametric technique to estimate the density functions, from Monte Carlo data, corresponding to different combination of mass sensitive parameters and type of primaries. These estimates are used to obtain the classification probability of protons and iron nuclei for the different combination of parameters considered. We find that, after considering all relevant fluctuations, the maximum classification probability obtained combining surface and fluorescence detectors parameters is of order of 90%.

Reconstruction of air shower muon densities using segmented counters with time resolution

“…It is easy to see that, ∂h ∂p j (p 1 = ξ, ..., p m−1 = ξ) = 0, (A. 6) which means that the vector p = (ξ, ..., ξ) is an extreme of h. Note that this property does not depend on the specific form of f . The elements of the Hessian matrix evaluated in this vector are given by, where δ i j is the Kronecker delta (δ ii = 1 and δ i j = 0 for i j).…”

“…At the highest cosmic ray energies the hadronic interactions are unknown, so models that extrapolate accelerator data at lower centre-of-mass energy are used in shower simulations. As the number of muons * Corresponding author: diego.ravignani@iteda.cnea.gov.ar predicted by simulations strongly depends on the assumed interaction model, the muon data can be used to discriminate among different scenarios [6,7,8,9,10].…”

Estimation of the number of muons with muon counters

“…The composition of the primary particle has to be inferred from different properties of the showers. The most sensitive parameters to the primary mass are the atmospheric depth at which the shower reaches its maximum development and the muon content of the showers [1,2,3]. In general, the muon density at a given distance to the shower axis is used in composition analyses.…”

A method for reconstructing the muon lateral distribution with an array of segmented counters with time resolution

“…At the highest cosmic ray energies the hadronic interactions are unknown, so models that extrapolate accelerator data at lower centre of mass energy are used in shower simulations. As the number of muons predicted by simulations strongly depends on the assumed high energy hadronic interaction model, the measurement of the muon component is also a very important tool to understand the hadronic interactions at cosmic ray energies [6].…”