R. R. Prado

Interpretation of measurements of the number of muons in extensive air shower experiments

Abstract In this paper we analyze the energy evolution of the muon content of air showers between 1018.4 and 1019.6 eV to be able to determine the most likely mass composition scenario from future number of muons measurements. The energy and primary mass evolution of the number of muons is studied based on the Heitler–Matthews model and Monte Carlo simulation of the air shower. A simple model to describe the evolution of the first and second moments of number of muons distributions is proposed and validated. An analysis approach based on the comparison between this model’s predictions and data to discriminate among a set of composition scenarios is presented and tested with simulations. It is shown that the composition scenarios can be potentially discriminated under the conditions imposed by the method. The discrimination power of the proposed analysis is stable under systematic changes of the absolute number of muons from model predictions and on the scale of the reconstructed energy.

MARTA: a high-energy cosmic-ray detector concept for high-accuracy muon measurement

A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers.

The study on the potential of muon measurements on the determination of the cosmic ray composition using a new fast simulation technique

In this work we study the energy evolution of the number of muons in air showers. Motivated by future plans for UHECR experiments, the analysis developed here focuses on how the evolution of the moments of the distributions of two shower observables, the depth of the shower maximum Xmax and the number of muons on the ground (Nm ), can be used to assess the validity of a mass composition scenario, surpassing the current uncertainties on the shower description. The cosmic ray composition is an essential ingredient for an astrophysical interpretation of the data. However, the inference of composition from air shower measurements is limited by the theoretical uncertainties on the high energy hadronic interactions. Statistical analyses using the energy evolution of different observables, like the moments of the Xmax and of the moments of the Nm distributions, can provide an efficient method to overcome these limitations providing more reliable information about the cosmic ray abundance. A new technique is presented here to generate a large set of simulated shower observables minimizing computer processing time. Fast algorithms to simulate the longitudinal development of the shower (i.e. CONEX) have longbeen available. However, the Nm is measured along the lateral development of the shower, which implies that three-dimensional simulations are needed (i.e. CORSIKA). This paper presents a parameterization of the main shower characteristics that can be used to simulate the number of muons on the ground using fast simulation algorithms. The parametrization was used to predict the evolution of log 10 Nm moments by possible hypothetic mass composition scenarios.