Air shower simulation programs are essential tools for the analysis of data from cosmic ray experiments and for planning the layout of new detectors. They are used to estimate the energy and mass of ...the primary particle. Unfortunately the model uncertainties translate directly into systematic errors in the energy and mass determination. Aiming at energies>10
19 eV, the models have to be extrapolated far beyond the energies available at accelerators. On the other hand, hybrid measurement of ground particle densities and calorimetric shower energy, as will be provided by the Pierre Auger Observatory, will strongly constrain shower models. While the main uncertainty of contemporary models comes from our poor knowledge of the (soft) hadronic interactions at high energies, also electromagnetic interactions, low-energy hadronic interactions and the particle transport influence details of the shower development. We review here the physics processes and some of the computational techniques of air shower models presently used for highest energies, and discuss the properties and limitations of the models.
The increasing cosmic ray statistics collected by present experiments and the future prospects with new large arrays demand accurate calculations of the extensive air shower (EAS) parameters. The ...energy of the primary particle is estimated by ground arrays fitting a lateral distribution function (LDF) to the particle densities at a given observing level. However, the lack of appropriate parameterization for these distributions, able to reproduce the data collected from all arrival directions, makes the experimental analysis difficult. We propose a method to parametrize particle density distributions of EAS at any incident zenith angle. Starting from analytical LDF for vertical showers we present a detailed study of the atmospheric depth dependence of the shower parameters. The results obtained are used to calculate the corresponding LDF for non-vertical showers including for the first time both, geometrical and atmospheric attenuation effects. We check the method analysing electron and muon LDF generated by Monte Carlo simulations from incident cosmic ray particles at different zenith angles. A comparison of the proposed LDF with experimental results, as well as MC data including detector effects, is also presented.
Azimuthal asymmetries in signals of non-vertical showers have been observed in ground arrays of water Cherenkov detectors, like Haverah Park and the Pierre Auger Observatory. The asymmetry in time ...distributions of arriving particles offers a new possibility for the determination of the mass composition. The dependence of this asymmetry on atmospheric depth shows a clear maximum at a position that is correlated with the primary species. In this work a novel method to determine mass composition based on these features of the ground signals is presented and a Monte Carlo study of its sensitivity is carried out.
Inelastic pp collisions are dominated by soft (low momentum transfer) physics, to which perturbative QCD cannot be fully applied. A deep understanding of both soft and semi-hard processes is crucial ...for predictions of minimum bias and underlying events of the pp large hadron collider (LHC) now coming on line. Moreover, the interaction of cosmic ray particles entering in the atmosphere is extremely sensitive to these soft processes and consequently cannot be formulated from first principles. Because of this, air shower analyses strongly rely on hadronic interaction models, which extrapolate collider data by several orders of magnitude. A comparative study of Monte Carlo simulations of pp collisions (at the LHC center-of-mass energy ≃14 TeV) using the most popular hadronic interaction models for ultrahigh energy cosmic ray (SIBYLL and QGSJET) and for collider physics (the PYTHIA multiparton model) is presented. The most relevant distributions are studied including the observables from diffractive events with the aim of discriminating between the different models.
The origin of the ultra high energy cosmic rays (UHECR) with energies above E > 1017eV, is still unknown. The discovery of their sources will reveal the engines of the most energetic astrophysical ...accelerators in the universe. This is a written version of a series of lectures devoted to UHECR at the 2013 CERN-Latin-American School of High-Energy Physics. We present an introduction to acceleration mechanisms of charged particles to the highest energies in astrophysical objects, their propagation from the sources to Earth, and the experimental techniques for their detection. We also discuss some of the relevant observational results from Telescope Array and Pierre Auger Observatory. These experiments deal with particle interactions at energies orders of magnitude higher than achieved in terrestrial accelerators.
A method is presented to extract the tau neutrino helicity, or equivalently, the chirality parameter
γ
va, independent of any tau polarization which may be present. The method is thus well-suited to ...measurements using taus produced from the Z
0 and is complementary to analyses using tau correlations since it provides the sign of the chirality parameter which is otherwise unavailable without recourse to lower energy experiments where taus are unpolarized. Results of Monte Carlo studies and comments regarding the use of the technique in experiments are also included.
A re-examination of the energy cosmic ray spectrum above 10
20 eV is presented. The overall data-base provides evidence, albeit still statistically limited, that non-nucleon primaries could be ...present at the end of the spectrum. In particular, the possible appearance of superheavy nuclei (seldom discussed in the literature) is analysed in detail.
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