Primary Mass Composition Research Articles

Measurements of the muon content of air showers at the Pierre Auger Observatory

The Pierre Auger Observatory offers a unique window to study cosmic rays and particle physics at energies above 3 EeV (corresponding to a centre-of-mass energy of 75 TeV in proton-proton collisions) inaccessible to accelerator experiments. We discuss the different methods of estimating the number of muons in showers recorded at the Pierre Auger Observatory, which is an observable sensitive to primary mass composition and to properties of the hadronic interactions in the shower. The muon content, derived from data with these methods, is presented and compared to predictions from the post-LHC hadronic interaction models for different primary composition. We find that models do not reproduce well the Auger observations, displaying a deficit of muons at the ground. In the light of these results, a better understanding of ultra-high energy extensive air showers and hadronic interactions is crucial to determine the composition of ultra-high energy cosmic rays. We report on the upgrade plans of the Pierre Auger Observatory to achieve this science goal.

Estimating of Cherenkov Radiation in Extensive Air Showers Using CORSIKA Code for Tunka133 EAS Cherenkov Array

The simulation of Cherenkov light Lateral distribution function (LDF) in Extensive Air Showers (EAS) initiated primary particles such as primary calcium, argon, proton iron nuclei, neutron and nitrogen have been performed using CORSIKA program for conditions and configurations of Tunka133 EAS Cherenkov array. The simulation was fulfilled at the high energy range 1014-1016eV for four different zenith angles 0o, 10o, 15oand 30o. The results of the simulated Cherenkov light LDF are compared with the measurements of Tunka133 EAS array for the same particles and energy range mentioned above. This comparison may give the good ability to reconstruct the energy spectrum and mass composition of the primary cosmic ray particles in EAS. The main feature of the given approach consists of the possibility to make a library of Cherenkov light LDF samples which could be utilized for analysis of real events which can be detected with different EAS arrays and reconstruction of the primary cosmic rays energy spectrum and mass composition of EAS particles.

Statistical methods for cosmic ray composition analysis at the Telescope Array Observatory

The Telescope Array surface detector stations record the temporal development of the signal from the extensive air shower front which carries information about the type of the primary particle. We develop the method to study the primary mass composition of the ultra-high-energy cosmic rays based on multivariate analysis (MVA). We report the preliminary mass composition results based on the Telescope array 5 years data.

Primary CR energy spectrum and mass composition by the data of Tunka-133 array

The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 · 10 15 -10 18 eV measured for 1540 hours of observation are presented.

Constraints and Measurements of Hadronic Interactions in Extensive Air Showers with the Pierre Auger Observatory

The characteristics of extensive air showers are sensitive to the details of hadronic interactions at energies and in kinematic regions beyond those tested by human-made accelerators. Uncertainties on extrapolations of the hadronic interaction models in these regions hamper the interpretation of the ultra high energy cosmic ray data in terms of primary mass composition. We report on how the Pierre Auger Observatory is able to constrain the hadronic interaction models by measuring the muon content and muon production depth of air showers and also by measuring the proton-air cross section for particle production at a center-of-mass energy per nucleon of 57 TeV.

Influence of hadron and atmospheric models on computation of cosmic ray ionization in the atmosphere—Extension to heavy nuclei

In the last few years an essential progress in development of physical models for cosmic ray induced ionization in the atmosphere is achieved. The majority of these models are full target, i.e. based on Monte Carlo simulation of an electromagnetic-muon-nucleon cascade in the atmosphere. Basically, the contribution of proton nuclei is highlighted, i.e. the contribution of primary cosmic ray α-particles and heavy nuclei to the atmospheric ionization is neglected or scaled to protons. The development of cosmic ray induced atmospheric cascade is sensitive to the energy and mass of the primary cosmic ray particle. The largest uncertainties in Monte Carlo simulations of a cascade in the Earth atmosphere are due to assumed hadron interaction models, the so-called hadron generators. In the work presented here we compare the ionization yield functions Y for primary cosmic ray nuclei, such as α-particles, Oxygen and Iron nuclei, assuming different hadron interaction models. The computations are fulfilled with the CORSIKA 6.9 code using GHEISHA 2002, FLUKA 2011, UrQMD hadron generators for energy below 80GeV/nucleon and QGSJET II for energy above 80GeV/nucleon. The observed difference between hadron generators is widely discussed. The influence of different atmospheric parametrizations, namely US standard atmosphere, US standard atmosphere winter and summer profiles on ion production rate is studied. Assuming realistic primary cosmic ray mass composition, the ion production rate is obtained at several rigidity cut-offs – from 1GV (high latitudes) to 15GV (equatorial latitudes) using various hadron generators. The computations are compared with experimental data. A conclusion concerning the consistency of the hadron generators is stated.

All-particle cosmic ray energy spectrum measured with 26 IceTop stations

We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, the surface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysis were taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122km2. The analysis investigated the energy spectrum from 1 to 100PeV measured for three different zenith angle ranges between 0° and 46°. Because of the isotropy of cosmic rays in this energy range the spectra from all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under different assumptions on the primary mass composition. Good agreement of spectra in the three zenith angle ranges was found for the assumption of pure proton and a simple two-component model. For zenith angles θ<30°, where the mass dependence is smallest, the knee in the cosmic ray energy spectrum was observed at about 4PeV, with a spectral index above the knee of about −3.1. Moreover, an indication of a flattening of the spectrum above 22PeV was observed.

NEVOD-DECOR experiment: results and future

Russian-Italian NEVOD-DECOR experiment on the measurements of the local muon density spectra (LMDS) at various zenith angles gave possibility to obtain information on primary cosmic ray flux and interaction characteristics in a record wide energy range from 1015 to more than 1018 eV. Comparison of the measurement results with CORSIKA-based simulations showed the increase of LMDS slope at PeV energies of primaries (corresponding to the first knee); a trend to a heavier primary mass composition above the knee; indication for a second knee (a further increase of the spectrum slope near 1017 eV). At large zenith angles and high muon densities (corresponding to primary energies around 1018 eV) a considerable excess of muon bundle events in comparison with the expectation based on independent estimates of the primary spectrum and widely used hadron interaction models has been found. In 2011, a new phase of measurements of the energy spectrum of cascade showers initiated by high-energy muons in water and of the energy deposit of muon bundles at various zenith angles and muon multiplicities started. Further plans include the deployment of a traditional EAS array around the NEVOD-DECOR complex.

Features of parameters of gamma-ray families formed from AA-interactions at superhigh energies above 1016 eV

Different lateral and energetic characteristics of gamma-ray families produced in nucleus-nucleus (AA) interactions of primary cosmic rays (PCR) are studied. Primary mass composition analysis performed on the basis of "Pamir" Collaboration X-ray emulsion chambers (XREC) data by using of selection criteria of gamma-ray families originating from AA-interactions above 10 PeV. Experimental data are compared with results of MC0 algorithm based on quark-gluon string model (QGSM). Among seven considered variables, only two lateral parameters, R1E and ρ, are not described by the MC0 model.

Estimating primary mass composition at energies 1017–1018 eV from EAS radio emission lateral distribution

Distribution of maximum depths of extensive air showers (EAS) with energies of 1017–1018 eV is restored from the lateral distribution of EAS radio emission measured by the LOPES experiment (40-80 MHz). Dependence of the EAS maximum depth on its energy is constructed and mass composition of cosmic rays is estimated. It follows from the obtained dependencies that the fraction of light cosmic ray's nuclei increases in the energy range under consideration.

Measurement of the proton-air cross-section with the Pierre Auger Observatory

We present the procedure to measure the proton-air cross-section at a center-of-mass energy per nucleon of 57TeV developed by the Pierre Auger Collaboration. The conversion from proton-air to inelastic proton-proton cross-section with an extended Glauber calculation is discussed. The systematic uncertainties of the analysis are summarized and the final result compared to accelerator data and model predictions. The growth of hadronic cross-sections towards ultra-high energies reflects changes in the internal structure of the colliding particles. Due to the nature of QCD it is still not possible to calculate hadronic cross-sections at ultra-high energies from first principles. It is thus of paramount importance to measure hadronic cross-sections in order to guide the development of phenomenological models needed to describe secondary multiparticle production at ultra-high energies. Such models are crucial, for example, for a detailed interpretation of available cosmic-ray air-shower data in terms of the primary mass composition. Without a better understanding of the cosmic-ray mass composition it will be very difficult to distinguish between different scenarios of cosmic-ray acceleration and propagation. We present the measurement of the proton-air cross-section with data of the Pierre Auger Observatory (1). The Pierre Auger Observatory is located close to the town of Malargue in Argentina. It consist of about 1660 water Cherenkov particle detector spread over a surface area of 3000km 2 .D uring clear and moonless nights the atmosphere on top of the surface array is overlooked by 27 fluorescence telescopes. This analysis is based on the observation of the longitudinal air-shower development with the telescopes. By combining the timing data of the surface detectors with that of the fluorescence telescopes a very precise reconstruction of the geometry is achieved (2). This technique is called hybrid reconstruction. It allows us a very accurate measurement of Xmax, the position at which an air-shower deposits the maximum energy per unit of mass of atmosphere traversed (3). With the precise observation of longitudinal air-shower fluctuations it is possible to achieve high sensitivity to the mean free path of the primary cosmic-ray particles and thus to the cross-section. This technique is well known and has been first applied by the Fly's Eye experiment (4). We also discuss systematic uncertainties and limitations of the cross-section measurement. In a last step, the proton-air cross-section measurement is converted into a proton-proton cross-section. This conversion makes use of a Glauber calculation, which has been extended to account for inelastic screening effects.

Application of statistical method for determination of primary mass composition of cosmic rays using simulated data

In this paper we have studied the reconstruction of primary mass composition based on simulated longitudinal shower development using a statistical method viz. the multiparametric topological analysis (MTA) and show its applicability for the determination of the primary mass composition. In particular, the sensitivity of X max distribution is tested for simulated data using CORSIKA-6990 code assuming a number of uniform and non-uniform mixed compositions of proton(p), oxygen(O) and iron(Fe) nuclei at primary energies 1017 eV and 1018 eV.

The non-linearity between [formula omitted] and [formula omitted] induced by the acceptance of fluorescence telescopes

The measurement of the average depth of the shower maximum is the most commonly used observable for the possible inference of the primary cosmic-ray mass composition. Currently, different experimental Collaborations process and present their data not in the same way, leading to problems in the comparability and interpretation of the results. Whereas 〈Xmax〉 is expected to be proportional to 〈lnA〉 in ideal conditions, we demonstrate that the finite field-of-view of fluorescence telescopes plus the attenuation in the atmosphere introduce a non-linearity into this relation, which is specific for each particular detector setup.

On the mass composition of primary cosmic rays in the energy region 1015–1016 eV

A method to determine the primary cosmic ray mass composition is presented. Data processing is based on the theoretical model representing the integral muon multiplicity spectrum as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. In the first stage, the permissible intervals of primary nuclei fractions fi are determined on the basis of the EAS spectrum versus the total number of muons (Eμ ⩾ 235 GeV). In the second stage, the permissible intervals of fi are narrowed by the fitting procedure. We use the experimental data on high multiplicity muon events (nμ ⩾ 114) collected at the Baksan underground scintillation telescope. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015–1016 eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03. The average logarithmic mass is lnA ≃ 1.93 and it is in good agreement with results before the knee energy obtained by JACEE, RUNJOB, ATIC. At energies above the knee (1015–1016 eV) our analysis supports KASCADE results and contradicts to CASA-BLANCA and DICE data.

On the mass composition of primary cosmic rays in the energy region 1015 – 1016 eV

The method of the determination of Primary Cosmic Ray mass composition is presented. Data processing is based on the theoretical model representing the EAS spectrum vs the total number of muons as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. At the first stage, the permissible intervals of primary nuclei fractions fi are determined on the base of the EAS spectrum vs the total number of muons (Eμ ≥ 235 GeV). At the second stage, the permissible intervals of fi are narrowed by fitting procedure. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015 – 1016 eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03.

Determination of Hadronic Interaction Characteristics with the Pierre Auger Observatory

The Pierre Auger Observatory measures extensive air showers (EAS) up to the highest energies. One of the biggest challenges in current data analyses is to interpret these data in terms of the primary mass composition. Due to the insufficient constraint of interactions in EAS this is afflicted with large uncertainties. On the other hand, this high sensitivity of EAS to interaction features can be exploited to determine or constrain properties of interactions up to of 450 TeV. We demonstrate how specific EAS observations are suited for this task and thus may contribute to limit the uncertainties in the interpretation of air showers. These are the estimation of the muon number at ground level and the study of the hadronic cross section for particle production via EAS fluctuations.

Underground hadronic calorimeter for EAS studies

An innovative method for studying the properties of extensive air showers (EASes) that is based on the detection of thermal neutrons generated by high energy hadrons under a soil absorber of 500 g cm−2 is proposed and tested. It is shown that underground hadronic calorimeter can be performed with special scintillation detectors developed by the authors. The method could be quite useful in gamma shower selection and investigations of EAS properties, primary cosmic ray mass composition, EAS core location, and so on.

A study of depth of shower maximum of simulated air shower longitudinal profile using statistical methods

The study of primary mass composition is important in revealing the vital information about the origin, acceleration and propagation mechanisms of high energy cosmic rays as it is difficult to analyse those properties directly. Several parameters may be considered for analysis of mass composition which carry information regarding the identity of the primary particle. The mass composition can be inferred from the study of depth of shower maximum ( X m a x ), shower maximum fluctuations ( Δ X m a x ) and elongation rate ( d X m a x / d E ). A new statistical analysis using higher moments of simulated air shower longitudinal profile using CORSIKA code within energy range 10 15 − 10 19 eV for different primary induced shower is presented here.

Model-insensitive approach to the cosmic ray primary mass composition deduction

We present new results for radial scale factors, R 0 , of the lateral distribution function of extensive air shower electrons. It is shown that difficulties in the direct experimental estimation of R 0 are no bar to primary mass composition deduction with weak sensitivity to hadronic interaction model implemented in calculations. Possibilities for more effective primary particles separation based on multi-component analysis are discussed.

Characterisation of the electromagnetic component in ultra-high energy inclined air showers

Inclined air showers – those arriving at ground with zenith angle with respect to the vertical θ > 60 ° – are characterised by the dominance of the muonic component at ground which is accompanied by an electromagnetic “halo” produced mainly by muon decay and muon interactions. By means of Monte Carlo simulations we give a full characterisation of the particle densities at ground in ultra-high energy inclined showers as a function of primary energy and mass composition, as well as for different hadronic models assumed in the simulations. We also investigate the effect of intrinsic shower-to-shower fluctuations in the particle densities.