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This paper investigates extensive air showers by estimating the muon and electron mean arrival time distributions at ultrahigh energies for various cosmic-ray particles. The Monte Carlo package AIRES (version 19.04.00) was used to perform simulations at energies of 1019 and 1020 eV. The influence of primary particles (p, 56Fe, and 16O), energies, and zenith angles (0°, 10°, and 20°) on the mean arrival time of muonic and electromagnetic shower disks created in an extensive air shower was examined. Parameterized mean arrival time distributions were calculated for secondary particles e-, e+, and μ, created by proton, iron, and oxygen nuclei at energy 1019 eV in a vertical shower. A polynomial function for these primaries in vertical showers was established using the results of this simulation. The results were compared with the KASCADE-Grande experiment and Sciutto's simulations at energy 1020 eV and θ = 0. In this work the construction of a database that can be used to compute the arrival time of elementary particles is crucial in ultra-high energy ranges through an analytic description between the time structure and the distance distribution.

The paper presents the results of long-term, continuous observations of the Cherenkov light at the Yakutsk array. The Cherenkov light measurements allow one to reconstruct the longitudinal development of the shower, which is associated with both the model of hadron interactions and the mass composition of cosmic rays. The paper also provides a review of the results that are important for the physics of air showers and the astrophysics of cosmic rays, obtained over a long period of time at the Yakutsk array. [ABSTRACT FROM AUTHOR]

This paper investigates extensive air showers by estimating the muon and electron mean arrival time distributions at ultrahigh energies for various cosmic-ray particles. The Monte Carlo package AIRES (version 19.04.00) was used to perform simulations at energies of 1019 and 1020 eV. The influence of primary particles (p, 56Fe, and 16O), energies, and zenith angles (0°, 10°, and 20°) on the mean arrival time of muonic and electromagnetic shower disks created in an extensive air shower was examined. Parameterized mean arrival time distributions were calculated for secondary particles e-, e+, and μ, created by proton, iron, and oxygen nuclei at energy 1019 eV in a vertical shower. A polynomial function for these primaries in vertical showers was established using the results of this simulation. The results were compared with the KASCADE-Grande experiment and Sciutto's simulations at energy 1020 eV and θ = 0. In this work the construction of a database that can be used to compute the arrival time of elementary particles is crucial in ultra-high energy ranges through an analytic description between the time structure and the distance distribution. [ABSTRACT FROM AUTHOR]

The CREDO-Maze project is the concept for a network of stations recording local, extensive cosmic ray air showers. Each station consists of four small scintillation detectors and a control unit that monitors the cosmic ray flux 24 h a day and transmits the results to the central server. The modular design of each array allows the results to be used in educational classes on nuclear radiation, relativistic physics, and particle physics and as a teaching aid in regular school classrooms and more. As an example, we present here some preliminary results from the CREDO-Maze muon telescope missions to the Arctic and down into a deep salt mine, as well as the first shower-particle correlation measurements from a table-top experiment at Walailak University. These experiments show that the different geometric configurations of the CREDO-Maze detector set can be used for projects beyond the scope of the secondary school curriculum, and they can form the basis of student theses and dissertations at universities. [ABSTRACT FROM AUTHOR]

Imaging atmospheric Cherenkov telescopes are used to record images of extensive area showers caused by high-energy particles colliding with the upper atmosphere. The images are analyzed to determine events' physical parameters, such as the type and the energy of the primary particles. The distributions of some of the physical parameters can be used as well, for example, to determine the properties of a gamma ray source. The key problem of any experiment is the calibration of experimental data. For this purpose, Monte Carlo simulated data with known values of the physical parameters are used. The main disadvantage of this method is its extremely high requirements for computing resources and the large amount of time spent on modelling. In this paper, we use an alternative approach: Cherenkov telescope images are simulated with conditional variational autoencoders. We compare the characteristics of both the individual images and their Hillas parameter distributions with those of the images generated by the Monte Carlo method. [ABSTRACT FROM AUTHOR]

The Tunka Advanced Instrument for gamma-ray and cosmic ray Astrophysics (TAIGA) is a hybrid observatory for the detection of extensive air showers (EAS), produced by high-energy gamma rays and cosmic rays. The complex consists of such facilities as TAIGA-IACT, TAIGA-HiSCORE, and a variety of others. The goal of the study is to introduce a deep learning-based technique for EAS axis reconstruction. A convolutional neural network (CNN) model is proposed, while HiSCORE events, consisting of time-amplitude data, are treated as images by the model. Reasoning behind the CNN model and model efficacy will be discussed, along with [preliminary] results for EAS axis direction determination. This article will show that the accuracy of the model reaches 1 –2 for the zenith and azimuthal angles, however, the accuracy of the model does not reach the accuracy of conventional methods. [ABSTRACT FROM AUTHOR]

This article is a brief biography and account of the scientific achievements of an inspiring Indian woman scientist, Dr Bibha Chowdhuri. Her story is one of courage, determination, and perseverance as she carved her path in a male dominated profession during a time when women faced severe obstacles even accessing basic education, let alone pursuing higher education and a career in science. [ABSTRACT FROM AUTHOR]

Ultra-high-energy (UHE, >0.1 PeV) γ-ray astronomy is rapidly evolving into an expanding branch of γ-ray astronomy with the surprising discovery of 12 PeVatrons and the detection of a handful of photons above 1 PeV. Nearly all known celestial object types that have emissions in the TeV band are found also to emit UHE photons. UHE γ-rays have a well-defined horizon inside our Galaxy due to the absorption of infrared and cosmic microwave backgrounds in the Universe. In the last 30 years, traditional cosmic ray (CR) measurement techniques have enabled the detection of UHE γ-rays and opened the last observation window. For leptonic sources, UHE radiation is in the deep Klein–Nishina regime, which is largely suppressed. Therefore, UHE γ-ray detection will be helpful in locating and identifying hadronic radiation sources, tracing the historic pursuit for the origin of CRs around the knee of the spectrum. The Crab Nebula is the focus of attention with measured photon emissions up to 1 PeV. In the absence of hadronic processes, these emissions may indicate the existence of an extreme accelerator of e+e−. Use of CR extensive air shower detection techniques broadens the field of view of the source observations, enabling measurement of UHE radiation surrounding the sources. These observations can probe the particle propagation inside and outside the accelerators and the subsequent injection/escape into the interstellar medium. [ABSTRACT FROM AUTHOR]

The device downscaling of electronic components has given rise to the need to consider specific failures in onboard airplane electronics. Single Event Effects (SEE) are a kind of failures that occur due to radiation in the atmosphere. For the purpose of ensuring onboard electronic reliability, there is a clear need for new tools to predict the SEE rate, at both avionic altitudes and at ground level. In this work, we develop a new tool: RAMSEES (Radiation Atmospheric Model for SEE Simulation), which simulates the atmospheric radiative environment induced by cosmic rays. This multiscale and multi-physics phenomenon is simulated using the Geant4 toolkit, allowing the creation of a database to characterize the radiation environment in the atmosphere as a function of altitude. We show the need to simulate very high-energy particles such as 100 TeV space protons, because they are the main contributor of radiation at avionic altitudes as well as at ground level. Our approach shows a good agreement with the experimental data, the standards, and other models, and it also points out some discrepancies, especially below 18 km of altitude. RAMSEES can be the basis of the estimation of the SEE rate from ground level to the stratosphere, at any given position and time. [ABSTRACT FROM AUTHOR]

High-energy physics in the atmosphere (HEPA) has undergone an intense reformation in the last decade. Correlated measurements of particle fluxes modulated by strong atmospheric electric fields, simultaneous measurements of the disturbances of the near-surface electric fields and lightning location, and registration of various meteorological parameters on the Earth have led to a better understanding of the complex processes in the terrestrial atmosphere. The cooperation of cosmic rays and atmospheric physics has led to the development of models for the origin of particle bursts recorded on the Earth's surface, estimation of vertical and horizontal profiles of electric fields in the lower atmosphere, recovery of electron and gamma ray energy spectra, the muon deceleration effect, etc. The main goal of this review is to demonstrate how the measurements performed at the Aragats cosmic ray observatory led to new results in atmospheric physics. We monitored particle fluxes around the clock using synchronized networks of advanced sensors that recorded and stored multidimensional data in databases with open, fast, and reliable access. Visualization and statistical analysis of particle data from hundreds of measurement channels disclosed the structure and strength of the atmospheric electric fields and explained observed particle bursts. Consequent solving of direct and inverse problems of cosmic rays revealed the modulation effects that the atmospheric electric field has on cosmic ray fluxes. [ABSTRACT FROM AUTHOR]

An array of five scintillation detectors has been installed in Sharif University of Technology to record extensive air showers. By using the time lags of the secondary particles of air showers relative to each other and the location of each of these particles relative to the core of the shower, the arrival direction of the primary particle producing each air shower has been obtained. These data show that the distribution of time intervals of successive events in all directions of arrival into the atmosphere is a random distribution. The distribution of the time intervals between successive events in different seasons has also been obtained and the seasonal effect has been investigated. The effects of the environment, including temperature and pressure, on the cosmic ray count rate have been investigated. The distribution of zenith and azimuth angles, as well as the solar, sidereal, and antisidereal time distributions of cosmic rays, have been obtained. [ABSTRACT FROM AUTHOR]

The complex EAS installation of the Tien Shan mountain cosmic ray station which is situated at a height of 3340 m above sea level includes the scintillation and Cherenkov detectors of charged shower particles, an ionization calorimeter and a set of neutron detectors for registering the hadronic component of the shower, and a number of underground detectors of the penetrative EAS component. Now it is intended to expand this installation with a promising method for detecting the radio-emission generated by the particles of the developing shower. The facility for radio-emission detection consists of a three crossed dipole antennae, one being set vertically, and another two - mutually perpendicularly in a horizontal plane, all of them being connected to a three-channel radio-frequency amplifier of German production. By the passage of an extensive air shower, which is defined by a scintillation shower detector system, the output signal of antenna amplifier is digitized by a fast multichannel DT5720 ADC of Italian production, and kept within computer memory. The further analysis of the detected signal anticipates its operation according to a special algorithm and a search for the pulse of radio-emission from the shower. A functional test of the radio-installation is made with artificial signals which imitate those of the shower, and with the use of a N1996A type wave analyzer of Agilent Technologies production. We present preliminary results on the registration of extensive air shower emission at the Tien Shan installation which were collected during test measurements.

The more correct recalculation from the measured Cherenkov light fluxes at distances of 200 (Q200) and 100 (Q100) m from the Extensive Air Shower (EAS) core to the energy of the primary particle has been developed using the results of M-C simulation by the CORSIKA code, assuming a light primary composition of cosmic rays. Using the new conversion expressions, a differential energy spectrum was obtained according to the data of the Tunka-133 array for 7 years of operation and the TAIGA-HiSCORE array for 2 years of operation. [ABSTRACT FROM AUTHOR]

The new type of EAS array consisting of EN-detectors possesses the ability to discriminate the composition of cosmic rays. At the Yangbajing Cosmic Ray Observatory, the PRISMA-16-YBJ array has been running for three years. We installed 16 so-called "sand cubes" with one cubic meter size, and compared the data obtained by placing PRISMA-16-YBJ on and away from the sand cubes to study the influence of target material, which is a major environmental factor, on the performance of the array. [ABSTRACT FROM AUTHOR]

In this paper, we present the concept of local networks of small extensive air shower arrays installed mainly in secondary schools. As part of the CREDO-Maze Project, we plan to equip as many schools as possible with sets of detectors capable of detecting extensive air showers and transmitting their data to the central CREDO Project server. The synergy of such a network will make it possible to create a CREDO "global detector" and carry out physical research sensu stricto, e.g., the search for the Gerasimova–Zatsepin effect or the Cosmic Ray Ensemble. The discovery of one or the other would have extremely important consequences for our understanding of the nature of very-high-energy cosmic rays. In this paper, we describe a prototype local mini-array built at our university and some of the results of the exemplary tests performed. The design of the station's electronics and the small size of the detectors allow it to be used to perform, with the simple addition of software, also other tasks within physics circles and student projects. The mini-array consists of four small detectors, with a simple system for triggering, recording, and online communication with the world. The station is designed for autonomous and continuous operation. [ABSTRACT FROM AUTHOR]

The device downscaling of electronic components has given rise to the need to consider specific failures in onboard airplane electronics. Single Event Effects (SEE) are a kind of failures that occur due to radiation in the atmosphere. For the purpose of ensuring onboard electronic reliability, there is a clear need for new tools to predict the SEE rate, at both avionic altitudes and at ground level. In this work, we develop a new tool: RAMSEES (Radiation Atmospheric Model for SEE Simulation), which simulates the atmospheric radiative environment induced by cosmic rays. This multiscale and multi-physics phenomenon is simulated using the Geant4 toolkit, allowing the creation of a database to characterize the radiation environment in the atmosphere as a function of altitude. We show the need to simulate very high-energy particles such as 100 TeV space protons, because they are the main contributor of radiation at avionic altitudes as well as at ground level. Our approach shows a good agreement with the experimental data, the standards, and other models, and it also points out some discrepancies, especially below 18 km of altitude. RAMSEES can be the basis of the estimation of the SEE rate from ground level to the stratosphere, at any given position and time.

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. [ABSTRACT FROM AUTHOR]

The observation of γ-ray sources above 100 TeV is one of the most intriguing fields in the investigation of the origin of cosmic rays. The YangBaJing Hybrid Array (YBJ-HA) experiment consist of scintillation detectors and underground muon detectors, the main objective is to measure gamma rays >10 TeV. In this study, we investigated an energy estimation method based on particle density and fixed distance from the shower axis by conducting a detailed Monte Carlo simulation of an extensive air shower using the YBJ-HA in Tibet. By comparing the results of the new method with those of other previously used estimators, we found that the new method can effectively improve the energy resolution of gamma rays. At an energy of 100 TeV for a zenith angle θ < 30°, the new energy estimation method has an improvement about 10% compared for the other estimators. [ABSTRACT FROM AUTHOR]

Cosmic rays, high-energy subatomic particles of extraterrestrial origin, are systematically measured by space-borne and ground-based instruments. A specific interest is paid to high-energy ions accelerated during solar eruptions, so-called solar energetic particles. In order to build a comprehensive picture of their nature, it is important to fill the gap and inter-calibrate ground-based and space-borne instruments. Here, we focus on ground-based detectors, specifically neutron monitors, which form a global network and provide continuous recording of cosmic ray intensity and its variability, used also to register relativistic solar energetic particles. The count rate of each neutron monitor is determined by the geomagnetic and atmospheric cut-offs, both being functions of the location. Here, on the basis of Monte Carlo simulations with the PLANETOCOSMICS code and by the employment of a new verified neutron monitor yield function, we assessed the atmospheric cut-off as a function of the altitude, as well as for specific stations located in the polar region. The assessed in this study altitude profile of the atmospheric cut-off for primary cosmic rays builds the basis for the joint analysis of strong solar proton events with different instruments and allows one to clarify recent definitions and related discussions about the new sub-class of events, so-called sub-ground-level enhancements (sub-GLEs). [ABSTRACT FROM AUTHOR]

Optimum distance is defined as a distance from the air -shower core in which the density of a number of particles calculated by the lateral distribution function at that distance has the least uncertainty. Furthermore, with a good approximation, this distance is independent of the characteristics of primitive ray and it only depends on the geometric shape of array . In this paper, by simulating 1000 vertical EAS of protons with the energy 300 TeV , using the CORSIKA Monte Carlo code and trigger condition, the calculated distance for the array triggering ALBORZ-1 was found to be equal to 9±1 m. Also, it was found that this distance as well as the density of the number of calculated particles was independent of the lateral distribution function used in the calculations

The astrophysical complex TAIGA (Tunka Advanced Instrument for cosmic-ray physics and Gamma-ray Astronomy), whose first phase is being completed in the Tunka valley 50 km from Lake Baikal, is described. Its research program, first results, and development prospects are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The first phase of the Alborz Observatory Array (Alborz-1) consists of 20 plastic scintillation detectors each one with surface area of 0.25 spread over an area of realized to the study of Extensive Air Showers around the knee at the Sharif University of Technology campus. The first stage of the project including construction and operation of a prototype system has now been completed and the electronics that will be used in the array instrument has been tested under field conditions. In order to achieve a realistic estimate of the array performance, a large number of simulated CORSIKA showers have been used. In the present work, theoretical results obtained in the study of different array layouts and trigger conditions are described. Using Monte Carlo simulations of showers the rate of detected events per day and the trigger probability functions, i.e., the probability for an extensive air shower to trigger a ground based array as a function of the shower core distance to the center of array are presented for energies above 1 TeV and zenith angles up to . Moreover, the angular resolution of the Alborz-1 array is obtained. For experimental study of the array, Alborz-1 sub-array consists of 5 detectors on a pentagon configuration similar to the central cluster of the Alborz-1 array have been collecting data since 2014 February for 14 month in 4th floor of physics department at Sharif University of Technology. Alborz-I, made of 20 scintillation detectors is set up in a cluster layout to study the cosmic ray spectrum in the energy range of 1012 to 1016 eV. . This paper reveals the zenith angle distribution function of detected air showers by this sub-array.

A novel cluster of sensitive detectors based on silicon photomultipliers (SiPM) is being developed for the Cherenkov gamma-ray telescope TAIGA-IACT (Tunka valley, Republic of Buryatia, Russia). The cluster will be able to detect Cherenkov radiation from extensive air showers in two wide bands: 250–300 nm (UV) and 250–700 nm (visible and UV). Each pixel consists of a Winston cone, 4 SiPMs with the total sensitive area of 144 mm2, and readout electronics based on fast analogue memory. During operation in the UV band, a UV-bandpass filter is used to suppress cluster sensitivity in the visible range. In order to evaluate the detection efficiency of the selected SiPMs, a specific software simulator of SiPM output signal has been developed. This simulator takes into account such inherent parameters of SiPMs as total number of microcells, their recharge time, the dark count rate, the effective detection area, the quantum efficiency, the crosstalk between microcells, as well as conditions of SiPM operation, namely, the background noise and the Ohmic load in the readout (front-end) electronics. With this simulator it is possible to determine the expected trigger threshold under given conditions and parameters of selected detectors. Based on preliminary simulations, OnSemi MicroFJ-60035 SiPM chips have been chosen for the novel cluster of TAIGA-IACT. These SiPMs have sensible efficiency in the ultraviolet range (5–20% in the 250–300 nm band) and are distinguished by the presence of a fast output, which allows one to capture a low amplitude signal above a relatively high background noise. [ABSTRACT FROM AUTHOR]

Cherenkov Telescope Array (CTA) is an upcoming instrument that will start a new generation of atmospheric Cherenkov telescopes. CTA is expected not only to provide an unprecedented sensitivity in the tens of GeV to hundreds of TeV range, but also to considerably improve the systematic uncertainties of the measurements. We study the images registered by Cherenkov telescopes from low energy gamma rays with its first interaction in the upper parts of the atmosphere. The images show a characteristic separation due to the deflection of the first e − e + pair in the Geomagnetic Field. We evaluate the performance of the standard stereoscopic analysis for such events. We derive also a novel method for energy estimation of V-shaped events based purely on geometrical properties of the image. We investigate the potential of combining the classical energy estimation and the novel method for independent validation of the systematic shifts in the energy scale of Cherenkov telescopes and discuss the limitations of such analysis. [ABSTRACT FROM AUTHOR]

The JEM-EUSO (Joint Experiment Missions for the Extreme Universe Space Observatory) program aims at developing Ultra-Violet (UV) fluorescence telescopes for efficient detections of Extensive Air Showers (EASs) induced by Ultra-High Energy Cosmic Rays (UHECRs) from satellite orbit. In order to demonstrate key technologies for JEM-EUSO, we constructed the EUSO-Balloon instrument that consists of a ∼1 m2 refractive telescope with two Fresnel lenses and an array of multi-anode photo-multiplier tubes at the focus. Distinguishing it from the former balloon-borne experiments, EUSO-Balloon has the capabilities of single photon counting with a gate time of 2.3 µs and of imaging with a total of 2304 pixels. As a pathfinder mission, the instrument was launched for an 8 h stratospheric flight on a moonless night in August 2014 over Timmins, Canada. In this work, we analyze the count rates over ∼2.5 h intervals. The measurements are of diffuse light, e.g. of airglow emission, back-scattered from the Earth's atmosphere as well as artificial light sources. Count rates from such diffuse light are a background for EAS detections in future missions and relevant factor for the analysis of EAS events. We also obtain the geographical distribution of the count rates over a ∼780 km2 area along the balloon trajectory. In developed areas, light sources such as the airport, mines, and factories are clearly identified. This demonstrates the correct location of signals that will be required for the EAS analysis in future missions. Although a precise determination of count rates is relevant for the existing instruments, the absolute intensity of diffuse light is deduced for the limited conditions by assuming spectra models and considering simulations of the instrument response. Based on the study of diffuse light by EUSO-Balloon, we also discuss the implications for coming pathfinders and future space-based UHECR observation missions. [ABSTRACT FROM AUTHOR]

An array including five scintillation detectors at Sharif University of Technology in Tehran (35 ° 4 3 ′ N, 51 ° 2 0 ′ E, 1200m a.s.l= 897 gcm−2), over a year from October 2016 to October 2017, collected more than 5. 6 × 1 0 5 extensive air shower (EAS) events in the energy range between 0.03PeV and 3PeV. Data from the array were used to examine the cosmic ray shadow of the Moon in the energy range mentioned. The observation of a deficit of cosmic rays in the direction of the moon can be an estimate of the accuracy of the measurement of the primary particles of the air showers. The deficit of cosmic rays from the direction of the moon, in fact, is due to the presence of the moon in the early direction of the cosmic rays which prevents them from reaching the earth, and is interpreted as the shadow of the moon. A preliminary analysis of the directions of cosmic rays has been done in a two-dimensional sky map (zenith and azimuth angles) to compare the deficit of cosmic rays in terms of the angular radius from the moving moon center with the centers randomly selected in the sky. In this method, a two-dimensional Gaussian distribution for shadowed events is considered, which the standard deviation of this distribution is interpreted as the angular resolution of the array. Also, using the CORSIKA simulation data, the angular resolution of this array is obtained for different energies and different zenith angles and its mean value is calculated by considering the probability of detecting different energies by the array. The angular resolutions obtained with these two methods are comparable. [ABSTRACT FROM AUTHOR]

Abstract The night time airglow is a dynamic phenomenon that acts as a background for the detection of the extensive air shower (EAS) fluorescence. It is a mandatory task to monitor this background for the ground-based telescopes and for the planned space-based telescopes, dedicated to observe the EAS events induced by the ultra-high energy cosmic rays. To perform this task, we have developed a one-pixel Airglow MONitor (AMON) instrument. This instrument provides the absolute intensities of the measured night sky background in the near-ultraviolet spectral range and in the one second temporal resolution. It is designed to be easily operated in different locations and so to offer required spatial resolution. The first results demonstrate that AMON data might be useful not only for the high-energy astrophysics purposes, but also for the studies of the airglow dynamics. [ABSTRACT FROM AUTHOR]

The Pierre Auger Observatory is currently the largest detector of cosmic rays of ultrahigh energies (from ∼1017 to ∼1020 eV). The size of its accumulated exposure and the hybrid concept of the detector have provided measurements of unprecedented precision on the cosmic ray energy spectrum, mass composition, and anisotropy searches. There is an ankle in the energy spectrum at ∼4 EeV and a steepening at the end of the energy spectrum (above ∼40 EeV). The mass composition around the ankle is mixed and is uncertain at the highest energies due to the lack of statistics and high systematic uncertainties coming from predictions of different models of hadronic interactions. These models have, moreover, serious problems in describing the muon component of air showers. Still, the mean mass number of cosmic rays reaches its lowest value at energy ∼2 EeV and increases gradually above this energy. A dipole in the arrival directions is observed for energies above 8 EeV at more than 5σ significance level. It points ∼125° from the Galactic center, indicating the extra‐Galactic origin of these cosmic rays. The correlation of the arrival directions with starburst galaxies disfavors the isotropy hypothesis at energies above ∼40 EeV at the 4σ level without penalization for the catalog scan. The Observatory is currently being upgraded to improve its sensitivity to the mass of cosmic rays at the highest energies, which is crucial to constrain their sources. [ABSTRACT FROM AUTHOR]

Abstract Very high energy gamma rays entering the atmosphere initiate Extensive air showers (EAS). The Cherenkov light induced by an EAS can be observed by ground-based telescopes to study the primary gamma rays. An important parameter of an EAS, determining its evolution, is the height of the first interaction of the primary particle. However, this variable cannot be directly measured by Cherenkov telescopes. We study two simple, independent methods for the estimation of the first interaction height. We test the methods using the Monte Carlo simulations for the 4 Large Size Telescopes (LST) that are part of the currently constructed Cherenkov Telescope Array (CTA) Observatory. We find that using such an estimated parameter in the gamma/hadron separation can bring a mild improvement (∼ 10 − 20 %) in the sensitivity in the energy range ∼ 30 − 200 GeV. [ABSTRACT FROM AUTHOR]

Abstract The Large High Altitude Air Shower Observatory (LHAASO), built 4410 m a.s.l. near Daocheng, in the Sichuan province of China, is a new-generation complex EAS array. The Square Kilometre Array (KM2A), one of LHAASO’s three detector arrays, is composed of 5195 electromagnetic particle detectors and 1171 muon detectors, which are distributed in an area of 1.3 km2. A lower trigger threshold would increase the number of low-energy showers detected, although this would also import many noise events because of the numerous KM2A detectors. In this work, the KM2A trigger logic adopted a software trigger system. A toy simulation was developed to estimate the chance coincidence rate of noise hits. Taking into account the characteristics of real cosmic ray shower events, the trigger logic was investigated by adjusting the space and time windows simultaneously using the detector simulation sample. In order to improve trigger efficiency and reduce the effect of noise, an optimized trigger criterion was achieved. The KM2A threshold energy can be reduced to 5 TeV. The performance of KM2A with this trigger criterion is presented. The expectation on observation of sun shadow and cosmic ray large-scale anisotropy are also shown. [ABSTRACT FROM AUTHOR]

Extensive air showers (EAS) are a cascade of electromagnetic radiation and ionized particles that produced in the atmosphere through the interaction of a primary cosmic ray with the atom's nucleus in the air producing a huge amount of secondary particles such as X-ray, electrons, neutrons, muons, alpha particles, etc. In this work, EAS effects were demonstrated by estimating the lateral distribution function (LDF) at ultrahigh energies of the various cosmic ray particles. The LDF of charged particles such as electron and positron pair production, gamma and muons particles was simulated at ultrahigh energies 1016, 1018 and 1019 eV. The simulation was carried out using an air shower simulator called AIRES system version 2.6.0. The effect of the primary particles, energies and zenith angle (θ) on the LDF of charged particles produced in the EAS was taken into account. Comparison of LDF for charged particles and experimental results gave good agreement for electron and positron pair production and muons particles at 1019eV for θ=0°. and 10°. [ABSTRACT FROM AUTHOR]

Abstract The GRAPES-3 experiment is a compact, high density extensive air shower (EAS) array of ∼ 400 scintillator detectors operating in conjunction with a 560 m2 tracking muon telescope with a threshold of E μ > 1 GeV. It is being operated in Ooty, India since 1 January 2000. The implementation of precise corrections for the effects of the variation in the pressure, and temperature of the atmosphere has permitted the muon telescope to deliver an accurate estimate of the intensity of the galactic cosmic rays (GCRs) as a function of direction. The muon telescope has been successfully used to study acceleration of muons during large thunderstorm events. The discovery of the transient weakening of Earth's magnetic field through the detection of a muon burst was undoubtedly the highlight of the GRAPES-3 experiment. At present the expansion of the muon telescope is ongoing to increase its area by 570 m2 to significantly enhance its capability. [ABSTRACT FROM AUTHOR]

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 × 10 13 eV–3 × 10 15 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, < τ i > = < t i − t p > , and the distribution of their mean standard deviations,  <  σ i  >  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. [ABSTRACT FROM AUTHOR]

Optimum distance (R) is a distance from the shower core in which the density calculated by lateral distribution function, has its minimum uncertainty. In this paper, using CORSIKA code, proton, carbon and iron primary in the energy range between 10-eV are simulated to find R for Alborz-I array located at an altitude of 1200m above sea level. It is shown that R is approximately independent of characteristics of primary particle and it is only dependent to array configuration. Dependency of R on layout and detector spacing for 20 Alborz-I array detectors, are studied. It is shown that the Alborz-I array layout and its detector spacing result into the best (minimum uncertainty) R for its number of detectors. In this work, R for Alborz-I array is obtained about m (from NKG function) and m (from NKG type function). In addition, it is shown that, by finding dependency of primary energy to density in optimum distance, energy of primary particle can be estimated well. An energy estimation function is suggested and the function is examined by another set of simulated showers. [ABSTRACT FROM AUTHOR]

The upcoming Cherenkov Telescope Array (CTA) project is expected to provide unprecedented sensitivity in the low-energy ( ≲ 100 GeV) range for Cherenkov telescopes. Most of the remaining background in this energy range results from misidentified hadron showers. In order to fully exploit the potential of the telescope systems it is worthwhile to look for ways to further improve the available analysis methods for γ /hadron separation. We study the composition of the background for the planned CTA-North array by identifying events composed mostly of a single electromagnetic subcascade or double subcascade from a π 0 (or another neutral meson) decay. We apply the standard simulation chain and state-of-the-art analysis chain of CTA to evaluate the potential of the standard analysis to reject such events. Simulations show a dominant role of such single subcascade background for CTA up to energies  ∼ 70 GeV. We show that a natural way of rejection of such events stems from a shifted location of the shower maximum, and that the standard stereo reconstruction method used by CTA already exploits most of expected separation. [ABSTRACT FROM AUTHOR]

Lateral distribution function of extensive air showers of energetic cosmic rays, indicate how secondary particles spread over a surface detectors. There are many different universal formulas between lateral distribution parameters and shower age parameter which can be used to infer about maximum development of extensive air shower (which is a key parameter to estimate the mass composition of primary cosmic rays). At present work, an estimated percent of mass composition of ultra-high energy cosmic rays is investigated by comparison between Ivanov et al. modeling of simulated data, which has been done by CoRSiKa, and Yakutsk experimental data. [ABSTRACT FROM AUTHOR]

The experimental γ-families in which events called 'halos' were detected using X-ray emulsion chambers (XRECs) of the PAMIR experiment are described. The halo nature is explained within the standard model of nuclear interactions. Based on events with halo, the fraction of p+He in primary cosmic rays (PCR) was estimated. It is shown that the PCR mass composition remains mixed in the range E = 1-100 PeV. [ABSTRACT FROM AUTHOR]

We present a novel method to measure precisely the relative spectral response of the fluorescence telescopes of the Pierre Auger Observatory. We used a portable light source based on a xenon flasher and a monochromator to measure the relative spectral efficiencies of eight telescopes in steps of 5 nm from 280 nm to 440 nm. Each point in a scan had approximately 2 nm FWHM out of the monochromator. Different sets of telescopes in the observatory have different optical components, and the eight telescopes measured represent two each of the four combinations of components represented in the observatory. We made an end-to-end measurement of the response from different combinations of optical components, and the monochromator setup allowed for more precise and complete measurements than our previous multi-wavelength calibrations. We find an overall uncertainty in the calibration of the spectral response of most of the telescopes of 1.5% for all wavelengths; the six oldest telescopes have larger overall uncertainties of about 2.2%. We also report changes in physics measurables due to the change in calibration, which are generally small. [ABSTRACT FROM AUTHOR]

Due to the high energy interactions of cosmic ray particles, progressive showers of secondary particles initiate in the atmosphere. Several models are suggested to describe the longitudinal development of extensive air showers, for example the Heitler model. The Heitler model also is written for hadronic showers. Anyhow, the predicted values of $X_{max}$ may differ significantly with the values from detailed simulations by up to about $100~(\mbox{g}/\mbox{cm}^{2})$ . In the present work, the mean depth of shower maximum is calculated using a variable interaction length. New equations for $X_{max} $ in the electromagnetic and hadronic showers have been obtained. [ABSTRACT FROM AUTHOR]

On the basis of detailed tables of signals from Yakutsk extensive air shower scintillation detectors that were calculated using the GEANT4 package, the numerical evaluation of the energy E of inclined extensive air showers has been obtained using a pilot signal at a distance of 1000 m from the shower axis and the known zenith angle θ using the CORSIKA package. This original estimate was obtained without using the method of cutting the signal spectra according to lines of equal intensity. We also obtained the values of practical units of measure for signals in ground-based and underground detectors. [ABSTRACT FROM AUTHOR]

Different high energy interaction models are the applied in CORSIKA code to simulate Extensive Air Showers (EAS) generated by Cosmic Rays (CR). In this work the effects of QGSJET01, QGSJETII, DPMJET, SIBYLL models on Xmax and multiplicity of secondary electrons and muons at observation level are studied.

Ultrahigh-energy cosmic rays interact with the Earth's atmosphere and produce great numbers of secondary particles forming an extensive air shower. These air showers emit radiation in the radio frequency range which delivers important information about the processes of radio emission in extensive air showers and properties of the primary cosmic rays, e.g. arrival direction, energy and mass with a duty cycle close to 100%. The radio extension of the world's largest cosmic-ray experiment, the Pierre Auger Observatory, is called the Auger Engineering Radio Array (AERA). In addition to the particle and fluorescence detectors of the Pierre Auger Observatory, AERA investigates the electromagnetic component of extensive air showers using 153 autonomous radio stations on an area of 17 km 2 . [ABSTRACT FROM AUTHOR]