Particles In Extensive Air Showers Research Articles

SWGO: a wide-field of view gamma-ray observatory in the southern hemisphere

Abstract The recent LHAASO and HAWC results opened the way to the search of gamma ray sources emitting at energies above 100 TeV. Both detectors are in the northern hemisphere; the need for such an observatory in the southern hemisphere is therefore clear. The goal of the SWGO collaboration is the construction of a wide field of view, high duty cycle observatory to explore the Southern hemisphere sky searching for gamma ray sources at energies above 100 GeV. Such an array will detect extensive air showers particles and must be able to select the photon originated showers from the background of the hadronic ones. The experiment must be located in a site at latitude between 10° and 30° degrees south and at an altitude above 4400 m a.s.l. The baseline detection technique chosen by the collaboration is Water Cherenkov Detectors. The array will have a central region with high fill factor (>60%) and a large (about 1 km2) outer region with a much lower fill factor (around 4–5%).

Performance comparison of water Cherenkov detectors with different geometries

In the framework of the development of the SWGO experiment, we have performed a detailed study of the single unit of an extensive air shower observatory based on an array of water Cherenkov detectors. Indeed, one of the possible water Cherenkov detector unit configurations for SWGO consists of tanks, and to reach a high detection efficiency and discrimination capability between gamma-ray and hadronic air showers, different tank designs are under investigation. In this study, we consider and compare double-layer tanks with several sizes, shapes and number of photo-multiplier tubes (PMTs). Muons, electrons, and gamma-rays with energies typical of secondary particles in extensive air showers have been simulated entering the tanks with zenith angles from 0 to 60 deg. The comparison between different tank geometries was evaluated considering the number of photoelectrons produced by the PMTs, the detection efficiency, and the time resolution of the measurement of the first photon. We will show that with circular and hexagonal tanks better performance can be obtained than with the square ones, and that it improves for smaller tanks as expected.

Exploring TeV Candidates of Fermi Blazars through Machine Learning

In this work, we make use of a supervised machine-learning algorithm based on Logistic Regression (LR) to select TeV blazar candidates from the 4FGL-DR2/4LAC-DR2, 3FHL, 3HSP, and 2BIGB catalogs. LR constructs a hyperplane based on a selection of optimal parameters, named features, and hyperparameters whose values control the learning process and determine the values of features that a learning algorithm ends up learning, to discriminate TeV blazars from non-TeV blazars. In addition, it gives the probability (or logistic) that a source may be considered a TeV blazar candidate. Non-TeV blazars with logistics greater than 80% are considered high-confidence TeV candidates. Using this technique, we identify 40 high-confidence TeV candidates from the 4FGL-DR2/4LAC-DR2 blazars and we build the feature hyperplane to distinguish TeV and non-TeV blazars. We also calculate the hyperplanes for the 3FHL, 3HSP, and 2BIGB. Finally, we construct the broadband spectral energy distributions for the 40 candidates, testing for their detectability with various instruments. We find that seven of them are likely to be detected by existing or upcoming IACT observatories, while one could be observed with extensive air shower particle detector arrays.

Muon Puzzle in Ultra-High Energy EASs According to Yakutsk Array and Auger Experiment Data

The lateral distribution of particles in extensive air showers from cosmic rays with energy above $10^{17}$ eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to the predictions obtained within frameworks of three ultra-high energy hadron interaction models. The cosmic ray mass composition estimated by the readings of surface-based and underground detectors of the array is consistent with results based on the Cherenkov light lateral distribution data. A comparison was made with the results of direct measurement of the muon component performed at the Pierre Auger Observatory. It is demonstrated that the densities of muon flux measured at Yakutsk array are consistent with results of fluorescent light measurements and disagree with results on muons obtained at the Auger array.

Muons in EASs with E0 = 1019 eV According to Data of the Yakutsk Array

Lateral distribution functions of particles in extensive air showers with the energy {{E}_{0}} approx {{10}^{{19}}}{kern 1pt} eV recorded by ground-based and underground scintillation detectors with a threshold of {{E}_{mu }} approx {kern 1pt} 1.0 times {text{sec}}{kern 1pt} theta GeV at the Yakutsk array during the continuous observations from 1986 to 2016 have been analyzed using events with zenith angles θ ≤ 60°. Experimental functions have been compared to the predictions obtained with the QGSJet-01-d hadron interaction model by applying the CORSIKA code. The entire dataset indicates that cosmic rays consist predominantly of protons.

An investigation on the rise time characteristics of particles in extensive air showers

Based on the CORSIKA simulations of inclined extensive air sowers with proton and iron as primary particles, we have calculated the rise time ( t 1 / 2 ) of detected pulses in particle detectors. We performed the simulations for six different zenith angles between 20° and 53°. It is shown that the rise time has a strong dependence on the core location, zenith, and azimuth angle of a primary particle. Moreover, azimuthal asymmetries of the rise time, which is a characteristic of inclined extensive air showers, are investigated. The potential use of this parameter for mass discrimination of cosmic rays is also discussed.

Performance test of the electromagnetic particle detectors for the LHAASO experiment

The Large High Altitude Air Shower Observatory (LHAASO) is a new generation hybrid cosmic ray observatory which is expected to reveal the mystery of the origin of cosmic rays. The one square kilometer array (KM2A) consisting of 5195 Electromagnetic particle Detectors (ED) and 1188 Muon Detectors (MD) is a sub-array of LHAASO. The EDs are designed to measure the density and arriving time of the secondary particles of extensive air showers. The performance of the EDs is tested for the quality control after construction in the laboratory at sea level. In this paper, the performance of more than four thousands EDs is summarized. The performance of all tested EDs meets the design requirements with the time resolution of 1.6 ns, the detection efficiency of 97.8%, charge resolution for single particle of 18.5% and count rate around 480 Hz. Furthermore, one ED is singled out for monitoring of the long-term stability over a period of nearly two years from December 2018 to November 2020.

Muon–Electron Pulse Shape Discrimination for Water Cherenkov Detectors Based on FPGA/SoC

The distinction of secondary particles in extensive air showers, specifically muons and electrons, is one of the requirements to perform a good measurement of the composition of primary cosmic rays. We describe two methods for pulse shape detection and discrimination of muons and electrons implemented on FPGA. One uses an artificial neural network (ANN) algorithm; the other exploits a correlation approach based on finite impulse response (FIR) filters. The novel hls4ml package is used to build the ANN inference model. Both methods were implemented and tested on Xilinx FPGA System on Chip (SoC) devices: ZU9EG Zynq UltraScale+ and ZC7Z020 Zynq. The data set used for the analysis was captured with a data acquisition system on an experimental site based on a water Cherenkov detector. A comparison of the accuracy of the detection, resources utilization and power consumption of both methods is presented. The results show an overall accuracy on particle discrimination of 96.62% for the ANN and 92.50% for the FIR-based correlation, with execution times of 848 ns and 752 ns, respectively.

An approach to identify the mass and energy of the primary cosmic rays around the knee region using arrival time distribution of secondary charged particles in extensive air showers

In this study a method will be presented to discriminate the mass and energy of the primary cosmic rays. This method uses the time distribution of secondaries in air showers originated from different primaries generated by CORSIKA Monte Carlo code at the Tehran 1200 m level (35°43′N, 51°20′E, 1200 m a.s.l).Simulations were performed for four primary energies (0.3, 1, 3 and 10 PeV) around the knee of cosmic ray spectrum. Three parameters of time distribution rise time, fall time and time of maximum were defined as mass and energy discriminator. By calculating Merit Factor(MF) ability of these parameters to discriminate mass and energy was evaluated. Heavy and light primary particles slightly separated in vertical 10 PeV showers by comparing time distribution’s fall time of secondary particles with MF = 1.68 ± 0.08 in 10 m from the shower core but for inclined showers this method does not work. In the same way, energy of primary particles also can be discriminated with one order of magnitude accuracy with MF = 2.17 ± 0.19 for showers with energy 0.3 and 3 PeV and MF = 2.09 ± 0.13 for showers with energy 1 and 10 PeV in 25 m 25 m from the shower core. In case of inclined showers, unlike mass discrimination their energies can be separated well. Effect of timing uncertainty of detectors on the ability of this method on energy discrimination is also studied. The results of this study can be applied in parallel with the common shower reconstruction techniques and other data analysis methods to improve estimation of high and ultra-high energy primary particle’s energy.

Cascade Particles in Extensive Air Showers with Energy Above 1017 eV According to Longstanding Measurements at the Yakutsk Array

Lateral distribution of cascade particles was studied in extensive air showers initiated by cosmic rays with energy above 1017 eV. The study is based on the data collected with ground-based scintillation detectors of the Yakutsk array during the continuous observational period from 1977 to 2017. Particle density measured in experiment is compared to the results of simulations performed for primary protons and iron nuclei within the framework of four ultra-high energy hadronic interaction models. Particle density obtained in the simulation was converted to signal of the scintillation detectors of the array. From the parameters of the resulted lateral distribution function, features of extensive air showers longitudinal development were derived.

Study on the detection efficiency and uniformity of a Water Cherenkov Detector based on Geant4

The Water Cherenkov Detector (WCD) is an important and widely used detector in cosmic ray physics, mainly used to measure the electromagnetic component of extensive air showers. Generally, a full detector simulation based on Geant4 for large arrays would require too much computing time and memory, because it would be a very CPU-intensive job to track all the Extensive Air Shower particles (mainly electrons and photons) hitting a very large area WCD detector. Therefore we developed a code simulating the behavior of muons, gamma-rays and electrons crossing a cell of a full WCD array. The results of this simulation can be collected in look-up table that can be used by fast simulation codes for large arrays. In this note we describe the results obtained simulating a single cell of cubic geometry (5×5×5 m3). The code we have developed for this particular geometry can easily be adapted to other detector designs. Firstly, the parameters in simulation are determined analysing the properties of the WCDs. Then, we calculate the most probable value (MPV) and sigma of the Landau function describing the distribution of the photoelectron numbers detected by the WCD photomultipliers. The results of the simulation are tested by a comparison with experimental results available in the literature: the relative error between their MPVs is only 1.37% for vertical muon- signal. We show that photoelectron distributions do not only depend on particle types and energies, but also on the incidence zenith angles and on the distance between the particle impact position and the center of the cell (i.e. the photomultiplier).

Mass Composition of Cosmic Rays with Energies Greater than 1017 eV, According to the Data from Surface Scintillation Detectors of the Yakutsk EAS Array

The spatial distribution of cascade particles in extensive air showers from cosmic rays with energies of E0 ≥ 1017 eV is studied at the Yakutsk array using surface scintillation detectors in continuous observations from 1977 to 2017. The experimental data are compared to calculations obtained with different models of hadron interactions. The mass composition of the cosmic rays changes from 〈lnA〉 ∼ 2.5 to the mass composition of protons in the energy range of (1–20) × 1017 eV.

On the efficiency of the evaluation of the primary cosmic ray composition using lateral distributions of air shower electromagnetic component

New analysis of lateral distributions (LD) of electrons, muons and charged particles in extensive air showers generated by 1015 − 1019 eV cosmic rays has been made with respect to the scaling formalism for LD and air shower universality paradigm. It is found that lateral distributions of electrons and muons, when considered separately, are well described by one-parametric scaling functions, while for the charged particles mixture distributions the scaling description is not accurate in radial distance range where electrons and muons give a comparable contribution to the local particle densities. The use of scaling formalism enables enhancing the electron/muon separation capabilities and, when combined with theoretically motivated air shower universality concept, provides robust mass composition estimates. The proposed approach could be implemented for the present and future (multi-) hybrid air shower observations, especially in realizing the potential of Auger and Telescope Array observatories upgrades, as well as for re-analysis and cross-calibration of the data collected from different air shower arrays in a broad primary energy range.

Very high energy astrophysics with the SHALON Cherenkov telescopes

Abstract The base of experiments using the imaging atmospheric Cherenkov telescopes is that the Cherenkov light emitted from the particles of extensive air shower created by the primary gamma-ray is collected by a mirror reflector and then detected by a pixelized PMT camera. SHALON are the imaging atmospheric Cherenkov telescopes created for the gamma-ray astronomy at the energies of 800 GeV to 100 TeV. Telescopes are located in the Tien-Shan mountains at the altitude of 3340 m a.s.l. The telescope systems have characteristics sufficient to record precise information about the shower structure in the energy range under consideration. SHALON experiment has been operating since 1992 and covers the wide astroparticle physics topics including an acceleration and origin of cosmic rays in supernova remnants , the physics of relativistic flaring objects like a black holes and active galactic nuclei as well as the long-term studies of the different type objects.

Composition of Cosmic Rays with E0 ⩾ 1017 eV Based on Data from the Ground Scintillation Detectors of the Yakutsk EAS Array

The lateral distribution of cascade particles in extensive air showers from cosmic rays with energy E0 ⩾ 1017 eV has been studied at the Yakutsk array by the ground scintillation detectors over the period of continuous observations 1977–2017. The experimental data are compared with those computed with various models for the development of extensive air showers from the CORSIKA software package. The best agreement between the theory and experiment is observed for the QGSjet-01-d model. In the energy range (1−20)× 1017 eV there is a change in the cosmic-raymass composition from 〈lnA〉 ≈ 2.5 to the proton one.

Observation of Anisotropy of TeV Cosmic Rays with Two Years of HAWC

Abstract After two years of operation, the High-Altitude Water Cherenkov (HAWC) Observatory has analyzed the TeV cosmic-ray sky over an energy range between 2.0 and 72.8 TeV. Like other detectors in the northern and southern hemispheres, HAWC observes an energy-dependent anisotropy in the arrival direction distribution of cosmic rays. This anisotropy is dominated by a dipole moment with phase in R.A. α ≈ 40° and amplitude that slowly rises in relative intensity from 8 × 10−4 at 2 TeV to 14 × 10−4 around 30 TeV, above which the dipole decreases in strength. A significant large-scale (>60° in angular extent) signal is also observed in the quadrupole and octupole moments, and significant small-scale features are also present, with locations and shapes consistent with previous observations. Compared to previous measurements in this energy range, the HAWC cosmic-ray sky maps improve on the energy resolution and fit precision of the anisotropy. These data can be used in an effort to better constrain local cosmic-ray accelerators and the intervening magnetic fields.

Simulation of the time structure of Extensive Air Showers with CORSIKA initiated by various primary particles at Alborz-I observatory level

A detailed simulation of showers with various zenith angles in atmosphere produced by different primary particles including gamma, proton, carbon, and iron at Alborz-I observatory level (35∘43′N, 51∘20′E, 1200 m a.s.l= 890 gcm−2), in the energy range 3 × 1013 eV–3 × 1015 eV, has been performed by means of the CORSIKA Monte Carlo code. The aim of this study is to examine the time structure of secondary particles in Extensive Air Showers (EAS) produced by the different primary particles. For each primary particle, the distribution of the mean values of the time delays of secondary particles relative to the first particle hitting the ground level in each EAS, <τi>=<ti−tp>, and the distribution of their mean standard deviations, < σi > in terms of distance from the shower core are obtained. The mean thickness and profile of showers as a function of their energy, primary mass, and zenith angle is described.

Radio emissions of extensive air showers with energies higher than 5 × 1018 eV at a frequency of 32 MHz according to measurements at the Yakutsk array

Results obtained from the measuring the radio emissions from extensive air shower particles with energies higher than 5 × 1018 eV at a frequency of 32 MHz are presented. A generalized formula is derived to describe the spatial distribution of radio emissions using the main EAS characteristics: energy Е 0 and depth of maximum development of shower Х max. The approximating function describes the data at average and large distances from a shower axis. The ratio of signal amplitudes at distances of 175 m and 725 m is used to determine Х max for an average shower with an energy of 1.54 × 1019 eV, which in our case is equal to Х max = 769 ± 34 g cm−2. Within the experimental error, the result for Х max is consistent with data obtained using EAS Cherenkov light.

Extensive air shower Monte Carlo modeling at the ground and aircraft flight altitude in the South Atlantic Magnetic Anomaly and comparison with neutron measurements

Modeling cosmic-ray-induced particle fluxes in the atmosphere is very important for developing many applications in aeronautics, space weather and on ground experimental arrangements. There is a lack of measurements and modeling at flight altitude and on ground in the South Atlantic Magnetic Anomaly. In this work we have developed an application based on the Geant4 toolkit called gPartAt that is aimed at the analysis of extensive air shower particle spectra. Another application has been developed using the MCNPX code with the same approach in order to evaluate the models and nuclear data libraries used in each application. Moreover, measurements were performed to determine the ambient dose equivalent rate of neutrons at flight altitude in different regions and dates in the Brazilian airspace; these results were also compared with the simulations.The results from simulations of the neutron spectra at ground level were also compared to data from a neutron spectrometer in operation since February 2015 at the Pico dos Dias Observatory in Brazil, at 1864m above sea level, as part of a collaboration between the Institute for Advanced Studies (IEAv) and the French Aerospace Lab (ONERA). This measuring station is being operated with support from the National Astrophysics Laboratory (LNA). The modeling approaches were also compared to the AtmoRad computational platform, QARM, EXPACS codes and with measurements of the neutron spectrum taken in 2009 at the Pico dos Dias Observatory.

A generalized description of the signal size in extensive air shower detectors and its applications

The number as well as the energy and angular distributions of particles in extensive air showers (EAS) depend on the stage of the shower development and the distance to the shower axis. In this work we derive an analytic parameterization of the particle distributions at ground from air shower simulations convolved with the response of a surface detector array. Shower particles are classified into four components according to the shower component they belong to: the muonic component, the electromagnetic component stemming from muon interactions and muon decay, the purely electromagnetic component, and the newly introduced electromagnetic component from low-energy hadrons. Using this scheme, we will show that the total signal at ground level for different surface detectors can be described with minimal fluctuations with parameterizations depending on the primary energy, position of the shower maximum, and the overall number of muons in the shower. The simulation results for different combinations of primaries and hadronic interaction models are reproduced with an accuracy better than 5–10% in the range from 100 m to 2000 m from the shower core. This parameterization is then used as a Lateral Distribution ansatz to reconstruct showers in current EAS experiments. Since this ansatz depends on physical parameters, it opens the possibility to infer them from data.