Comparing the signals measured by the surface and underground scintillator detectors of the Yakutsk Extensive Air Shower Array, we place upper limits on the integral flux and the fraction of primary cosmic-ray photons with energies E > 10^18 eV, E > 2*10^18 eV and E > 4*10^18 eV. The large collected statistics of the showers measured by large-area muon detectors provides a sensitivity to photon fractions < 10^-2, thus achieving precision previously unreachable at ultra-high energies.
Lateral distribution of muons in extensive air showers registered at the Yakutsk array was investigated. The analysis covers two periods of observation: before 2018 and after 2020, when the revision of muon detectors with 1-GeV threshold was complete. Measured values of muon density are compared to computational results obtained within the framework of two hadron interaction models. Within the energy domain above $10^{18}$ eV the best agreement is observed for proton composition primary cosmic rays.
Characteristics of the muon component in EAS are analyzed together with their fluctuations. The aim of this analysis -- a comparison of experimental data with computational results obtained within frameworks of various hadron interaction models for protons and iron nuclei and an estimation of cosmic ray mass composition in the ultra-high energy region.
The lateral distribution of muons with ~1.0x\sec(θ) GeV in extensive air showers within ~10^{17}-10^{19} eV energy region obtained during different observational periods from November 1987 to June 2013 has been analyzed. Experimental data have been compared to predictions of various hadron interaction models. The best agreement is observed with QGSJETII-04. Until 1996, the mass composition of cosmic rays with energy below 2x10^{18} eV was significantly lighter than in later periods.
The lateral distribution of muons with threshold energy e ~ 1*sec(theta) GeV have been studied in showers with energy E>=10^17 eV. The data considered in the analysis have been collected from November 2011 to June 2013. Experimental values are compared to predictions obtained with the use of CORSIKA code within the framework of various hadron interaction models. The best agreement between experiment and theory is observed for QGSJETII-04 model. At E~10^17 eV it complies to a mixed cosmic ray composition with the mean atomic number <lnA>~3.0+/-0.5. At E>= 4*10^17 eV the composition varies aroun…
Cherenkov light lateral distribution function (CLLDF) in Extensive Air Showers (EAS) for different primary particles (e-, n , p, F, K and Fe) was simulated using CORSIKA code for conditions and configurations of Yakutsk EAS array with the fixed primary energy 3 PeV around the knee region at different zenith angles. Basing on the results of CLLDF numerical simulation, sets of approximated functions are reconstructed for different primary particles as a function of the zenith angle. A comparison of the parameterized CLLDF with that simulated with Yakutsk EAS array is verified. The parameterized …
Responses of surface and underground scintillation detectors of Yakutsk array are calculated for showers initiated by primary particles with energy E0>=1.0E17 eV within the frameworks of QGSJet01 QGSIIJet-II-04, SIBYLL-2.1 and EPOS-LHC hadron interaction models. A new estimation of E0 is obtained with the use of various methods. The resulting energy is lower compared to the obtained with earlier method by factor ~1.33.
The arrival directions of ultrahigh energy extensive air showers (EAS) by Yakutsk, AGASA and P. Auger data are considered. It is found that the arrival directions of EAS with a deficit muons by Yakutsk data are not isotropy. Majority of these EAS form doublets which have maximum at side anticenter of Galaxy. It is shown that some EAS by data of Yakutsk, AGASA, P.Auger correlate with pulsars. These pulsars are situated near Input and Output Local arm Galaxy Orion. The majority of these pulsars have a short period rotate around of their axes. The problem of cosmic ray origin is discussed.
The energies of the most energetic extensive air showers observed at the Yakutsk array have been estimated with help of the all detectors readings instead of using of the standard procedure with a parameter s(600). The energy of the most energetic extensive air shower observed at the Yakutsk array happened to be 200, 200, 180 and 165 EeV with the values of the Xi**2 function per one degree of freedom 0.9, 1., 0.9 and 1.1 for the primary protons and helium, oxygen and iron nuclei accordingly.
Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of $E_0 \ge 10^{17}$ eV over the period of continuous observations from 1974 to 2017 are presented. A refined expression for estimating the primary-particle energy is used for individual events. This expression is derived from calculations aimed at determining the responses of the ground-based and underground scintillation detectors of the Yakutsk array for studying extensive air showers (EAS) and performed within the QGSJET01, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHC models by employing the CORSI…
The paper presents data on the muon component with a threshold \(\varepsilon_{thr} \geq\) 1 GeV. Air showers were registered at the Yakutsk array during almost 50 years of continuous air shower observations. The characteristics of muons are compared with calculations of QGSjetII-04 and EPOS LHC models for a proton and an iron nucleus. There is a muon deficit in the models, at energies greater than 5 EeV. To make an agreement between experimental data and simulations on muons, further tuning of the models is required.
The energy spectrum of cosmic rays in the range 10^15 eV to 6*10^19 eV has been studied using the air Cherenkov light detectors of the Yakutsk array. The total flux of photons produced by relativistic electrons (including positrons as well, hereafter) of extensive air showers in the atmosphere is used as the energy estimator of the primary particle initiating a shower. The resultant differential flux of cosmic rays exhibits, in accordance with previous measurements, a knee and ankle features at energies 3*10^15 and ~10^19 eV, respectively. A comparison of observational data with simulations is…
The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world's largest ground-based instruments aimed at studying the properties of cosmic rays in the ultra-high energy domain. In this report we discuss results recently obtained at the array - on cosmic rays energy spectrum, mass composition and directional anisotropy - and how they fit into the world data. Special attention is paid to the measurements of muonic component of extensive air showers. Theoretical results of particle acceleration at shocks …
Some discrepancies have been reported between observed and simulated muon content of extensive air showers: the number of observed muons exceeded the expectations in HiRes-MIA, Yakutsk and Pierre Auger Observatory data. Here, we analyze the data of the Moscow State University Extensive Air Shower (EAS-MSU) array on E_mu>~10 GeV muons in showers caused by ~(10^17-10^18) eV primary particles and demonstrate that they agree with simulations (QGSJET-II-04 hadronic interaction model) once the primary composition inferred from the surface-detector data is assumed.
Results are presented that were obtained by analysing the arrival directions of E0 > 8x10**18 eV primary cosmic rays recorded at the Yakutsk array over the period between 1974 and 2003 and at the SUGAR array (Australia). The greatest primary cosmic ray flux is shown to arrive from the region of visible intersection of the planes of the Galaxy and the Supergalaxy (local supercluster of galaxies) at a galactic longitude of about 137 degres. On a global scale, the lowest temperature of the cosmic microwave background is typical of this region.
The distribution of the muon content of highly inclined Monte Carlo cosmic ray showers is affected by the influence of Earth's geomagnetic field. It is found that the shapes of the positive and negative muon distributions get affected/modified by the influence of the Earth's geomagnetic field. Such a correlation between the earth's geomagnetic activity and the cosmic ray (CR) air shower muons is found sensitive to the primary cosmic ray mass composition.
New developments in detector technology allow for a realistic cost of large area surface detectors for cosmic ray air showers, with some limitations on particle identification, energy resolutions, directional information and dynamic range. In this paper, we present a simulation study using CORSIKA to quantify the lateral profile of the muons at ground level, characterized by their energy spectrum and lateral spread, and combine it with the depth at shower maximum (X$_{max}$) of an EAS initiated by a primary at energies $10^{16}$ eV - $10^{19}$ eV. Using different primaries, we show that the co…
In order to examine a muon excess observed by the Pierre Auger Observatory, detailed Monte Carlo simulations were carried out for primary protons, iron nuclei and strangelets (hypothetical stable lumps of strange quark matter). We obtained a rough agreement between the simulations and the data for ordinary nuclei without any contribution of strangelets in primary flux of cosmic rays. Our simulations suggest that the shower observables are dominated by details of hadronic interaction models.
The method of a determination of 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. At the first stage, the permissible intervals of primary nuclei fractions f_i are determined on the base of the EAS spectrum vs the total number of muons (E_mu > 235 GeV). At the second stage, the permissible intervals of f_i are narrowed by fitting procedure. We use the experimental da…
In this work we examine with the help of Monte Carlo simulation whether a consistent primary energy spectrum of cosmic rays emerges from both the experimentally observed total charged particles and muon size spectra of cosmic ray extensive air showers considering primary composition may or may not change beyond the knee of the energy spectrum. It is found that EAS-TOP observations consistently infer a knee in the primary energy spectrum provided the primary is pure unchanging iron whereas no consistent primary spectrum emerges from simultaneous use of the KASCADE observed total charged particl…
IceTop is the surface instrumentation of the IceCube Neutrino Observatory at the South Pole. It is designed to measure extensive air showers of cosmic rays in the primary energy range from PeV to EeV. Air showers induced by heavier primary particles develop earlier in the atmosphere and produce more muons observable at ground level than lighter cosmic rays with the same primary energy. Therefore, the fraction of muons to all charged particles measured by IceTop characterizes the mass of primary particles. This analysis seeks a muon-based mass sensitive parameter by using the charge signal dist…
The Sydney University Giant Air-shower Recorder (SUGAR) measured the energy spectrum of ultra-high-energy cosmic rays reconstructed from muon-detector readings, while the Pierre Auger Observatory, looking at the same Southern sky, uses the calorimetric fluorescence method for the same purpose. Comparison of their two spectra allows us to reconstruct the empirical dependence of the number of muons in the shower on the primary energy for energies between $10^{17}$ and $10^{18.5}$ eV. We compare this dependence with the predictions of hadronic interaction models \mbox{QGSJET-II-04} and \mbox{EPOS…
The IceCube Neutrino Observatory at the South Pole can provide unique tests of muon production models in extensive air showers by measuring both the low-energy (GeV) and high-energy (TeV) muon components. We present here a measurement of the TeV muon content in near-vertical air showers detected with IceTop in coincidence with IceCube. The primary cosmic-ray energy is estimated from the dominant electromagnetic component of the air shower observed at the surface. The high-energy muon content of the shower is studied based on the energy losses measured in the deep detector. Using a neural netwo…
In this work, the effects of the extensive air showers (EAS) were described by estimating the lateral distribution function (LDF) at very high energies of various cosmic ray particles. LDF was simulated for charged particles such as the electron and positron pair production, gamma, muons and all charged particles at very high energies 10^16, 10^18 and 10^19 eV. The simulation was performed using air shower simulator system (AIRES) version 2.6.0. The effect of primary particles, energies, thinning energy and zenith angle on the charged LDF particles produced in the EAS was taken into account. T…
We put together the experimental results on muon component of extensive air showers (EAS) which were gained with various techniques at the detector complex of the Tien Shan mountain station. According to this comparison, the problem of the EAS muon content in the range of primary cosmic ray energies (1-100)PeV seems to be more complicated than it was usually supposed. Generally, from the models of nuclear interaction it follows that the EAS which have produced gamma-hadron families in the Tien Shan X-ray emulsion chamber did preferably originate from interaction of the light cosmic ray nuclei,…
The production spectrum of high-energy muons as a function of depth in the atmosphere is relevant for understanding properties of event rates in deep detectors. For a given atmospheric profile, cascades of heavy nuclei develop at higher altitude than proton showers, giving rise to larger separation of muons at depth. For a given type of primary cosmic ray, seasonal variations in muon rates reflect the fact that higher temperatures correspond to lower densities and to a relative increase in the ratio of decay to re-interaction of the parent mesons. In this paper, we present a generalization of …
Production of high-energy muons in cosmic-ray air showers, relevant for underground detectors, depends on the properties of the primary cosmic ray as well as the atmospheric temperature through the competition between decay and re-interaction of charged pions and kaons. We present a parameterization of muon production profiles based on simulations as a function of the primary cosmic-ray energy, mass and zenith angle, the minimum energy for a muon to reach the detector and an atmospheric temperature profile. We illustrate how this can be used to calculate muon bundle properties such as multipli…
The production of very high energy muons inside an extensive air shower is observable at $ν$ telescopes and sensitive to the composition of the primary cosmic ray. Here we discuss five different sources of these muons: pion and kaon decays; charmed hadron decays; rare decays of unflavored mesons; photon conversion into a muon pair; and photon conversion into a $J/ψ$ vector meson decaying into muons. We solve the cascade equations for a $10^{10.5}$ GeV proton primary and find that unflavored mesons and gamma conversions are the two main sources of $E\ge 10^{8.5}$ GeV muons, while charm decays d…
IceCube, with its surface array IceTop, detects three different components of extensive air showers: the total signal at the surface, GeV muons in the periphery of the showers and TeV muons in the deep array of IceCube. The spectrum is measured with high resolution from the knee to the ankle with IceTop. Composition and spectrum are extracted from events seen in coincidence by the surface array and the deep array of IceCube. The muon lateral distribution at the surface is obtained from the data and used to provide a measurement of the muon density at 600 meters from the shower core up to 30 Pe…
We explore the feasibility of estimating primary cosmic ray composition at high energies from the study of two parameters of Extensive Air Showers (EAS) at ground and underground level with Monte Carlo simulations using the new EPOS and QGSJETII hadronic models tuned with LHC data. Namely, the slope and density at a given distance of the muon lateral distribution function are analysed in this work. The power to discriminate primary masses is quantified in terms of merit factor for each parameter. The analysis considers three different primary particles (proton, iron and gamma), four different …
Competition between decay and re-interaction of charged pions and kaons depends on the temperature/density profile of the upper atmosphere. The amplitude and phase of the variations depend on the minimum muon energy required to reach the detector and on muon multiplicity in the detector. Here we compare different methods for characterizing the muon production profile and the corresponding effective temperature. A muon production profile based on a parameterization of simulations of muons as a function of primary energy is compared with approximate analytic solutions of the cascade equation int…
The origin and nature of the cosmic rays is still uncertain. However, a big progress has been achieved in recent years due to the good quality data provided by current and recent cosmic-rays observatories. The cosmic ray flux decreases very fast with energy in such a way that for energies $\gtrsim 10^{15}$ eV, the study of these very energetic particles is performed by using ground based detectors. These detectors are able to detect the atmospheric air showers generated by the cosmic rays as a consequence of their interactions with the molecules of the Earth's atmosphere. One of the most impor…
In the present work we carry out a study of the high energy cosmic rays mass identification capabilities of a hybrid detector employing both fluorescence telescopes and particle detectors at ground using simulated data. It involves the analysis of extensive showers with zenith angles above 60 degrees making use of the joint distribution of the depth of maximum and muon size at ground level as mass discriminating parameters. The correlation and sensitivity to the primary mass are investigated. Two different techniques - clustering algorithms and neural networks - are adopted to classify the mas…
We present two new aspects of Extensive Air Shower (EAS) development universality allowing to make accurate estimation of muon and electromagnetic (EM) shower contents in two independent ways. In the first case, to get muon (or EM) signal in water Cherenkov detectors it is enough to know the vertical depth of shower maximum and the total signal. In the second case, the EM signal can be calculated from the primary particle energy and the zenith angle. In both cases the parameterizations of muon and EM signals are almost independent on primary particle nature, energy and zenith angle.
The main goal of the Andyrchy-BUST experiment is to study the primary cosmic rays spectrum and composition around the knee. The experimental data on the knee, as observed in the electromagnetic and high energy muon components, are presented. The electromagnetic component in our experiment is measured using the "Andyrchy" EAS array. High energy muon component (with 230 GeV threshold energy of muons) is measured using the Baksan Underground Scintillation Telescope (BUST). The location of the "Andyrchy" right above the BUST gives us a possibility for simultaneous measurements of both EAS componen…
The KASCADE-Grande Muon Tracking Detector enables with high accuracy the measurement of directions of EAS muons with energy above 0.8 GeV and up to 700 m distance from the shower centre. Reconstructed muon tracks are used to investigate muon pseudorapidity (eta) distributions. These distributions are nearly identical to the pseudorapidity distributions of their parent mesons produced in hadronic interactions. Comparison of the eta distributions from measured and simulated showers can be used to test the quality of the high energy hadronic interaction models. In this context a comparison of the…
ALICE, a general purpose experiment designed to investigate nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC), has also been used to detect atmospheric muons produced by cosmic-ray interactions in the atmosphere. In this contribution the analysis of the multiplicity distribution of the atmospheric muons detected by ALICE between 2010 and 2013 is presented, along with a comparison with Monte Carlo simulations. Special emphasis is given to the study of high-multiplicity events, i.e. those containing more than 100 reconstructed muons. Such high-multiplicity events demand primary …
In extensive air shower experiments, the number of muons crossing a detector at a given position, as well as their arrival time, arrival direction, and energy, are determined by a more fundamental 3-dimensional distribution linked to the hadronic core of the shower. Muons are produced high up in the atmosphere after the decay of mesons in the hadronic cascade. The distributions of production depth, energy, and transverse momentum of muons are enough to fully predict the muon component of air showers in any particular observational condition. By using air-shower simulations with the state-of-th…
The mass composition of ultra-high energy cosmic rays can be studied from the distributions of the depth of shower maximum and/or the muon shower size. Here, we study the dependence of the mean muon shower size on the depth of shower maximum in detail. Air showers induced by protons and iron nuclei were simulated with two models of hadronic interactions already tuned with LHC data (run I-II). The generated air showers were combined to obtain various types of mass composition of the primary beam. We investigated the shape of the functional dependence of the mean muon shower size on the depth of…
The recent observations of muon charge ratio up to about 10 TeV and of atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed interest into the high-energy interaction models and cosmic ray primary composition. A reviewed calculation of lepton spectra produced in cosmic-ray induced extensive air showers is carried out with a primary cosmic-ray spectrum that fits the latest direct measurements below the knee. In order to achieve this, we used a full Monte Carlo method to derive the inclusive differential spectra (yields) of muons, muon neutrinos and electron neutrinos at …
The data of cosmic ray NEVOD-DECOR experiment on the investigation of inclined muon bundles for a long time period (May 2012 - March 2021) are presented. The analysis showed that the observed intensity of muon bundles at primary cosmic ray energies of about 1 EeV and higher can be compatible with the expectation in frame of widely used hadron interaction models only under the assumption of an extremely heavy mass composition. This conclusion is consistent with data of several experiments on investigations of muon content in air showers, but contradicts the available fluorescence data on Xmax w…
The ratio of the number of muons with a threshold of 1 GeV and charged particles at a distance of 600 m from the axis is analyzed. Air showers with energies above 5 EeV and zenith angles with less than 60 degrees are considered. Comparison of experimental data with calculations by the QGSJETII-04 model for various primary nuclei, including a gamma ray, showed that the mass composition of cosmic rays up to energies of $\sim$ 10 EeV mainly consists of protons and helium nuclei, with a small number of heavy nuclei. Data include air showers with a very low muon content, which are assumed to be pro…
New analysis of lateral distributions (LD) of electrons, muons and charged particles in extensive air showers generated by $10^{15}-10^{19}$ 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 de…
The HAWC (High Altitude Water Cerenkov) gamma ray observatory observes muons with nearly-horizontal trajectories corresponding to zenith angles greater than $80^{0}$. HAWC is located at an altitude of 4100 meters a.s.l. (70 deg. atmospheric depth of 2400 g/cm$^{2}$) on the extinct volcano, Sierra Negra in Mexico. In this poster, we summarize the CORSIKA and GEANT4 as well as toy-model based simulations performed to determine the effective area of HAWC to muons from high zenith angle cosmic ray primaries. We are developing an updated GEANT4 based detector response simulation that includes a mod…
Recent results obtained from leading cosmic ray experiments indicate that simulations using LHC-tuned hadronic interaction models underestimate the number of muons in extensive air showers compared to experimental data. This is the so-called muon deficit problem. Determination of the muon component in the air shower is crucial for inferring the mass of the primary particle, which is a key ingredient in the efforts to pinpoint the sources of ultra-high energy cosmic rays.In this paper, we present a new method to derive the muon signal in detectors, which uses the difference between the total re…
Simulations of extensive air showers using current hadronic interaction models predict too small numbers of muons compared to events observed in the air-shower experiments, which is known as the muon-deficit problem. In this work, we present a new method to calculate the factor by which the muon signal obtained via Monte-Carlo simulations must be rescaled to match the data, as well as the beta exponent from the Heitler-Matthews model which governs the number of muons found in an extensive air shower as a function of the mass and the energy of the primary cosmic ray. This method uses the so-cal…
Change of the energy characteristics of muon bundles with an increase of the primary cosmic ray particles energy can be a key to solving the problem of muon excess in the extensive air showers (EAS) observed in a number of experiments. In this work the data on the energy deposit of multi-muon events in a wide range of zenith angles (and as a consequence in a wide range of primary particles energies) obtained with NEVOD-DECOR setup over a long time period are presented. The experimental data are compared with the results of simulations of EAS muon component performed using CORSIKA code.
The combined information from cosmic ray air showers that trigger both the surface and underground parts of the IceCube Neutrino Observatory allows the reconstruction of both the energy and mass of the primary particle through the knee region of the energy spectrum and above. The properties of high-energy muon bundles, created early in the formation of extensive air showers and capable of penetrating deep into the ice, are related to the primary energy and composition. New methods for reconstructing the direction and composition-sensitive properties of muon bundles are shown. Based on a likeli…
The fluxes of electrons, positrons, gammas, Cherenkov photons and muons in individual extensive air showers induced by the primary protons and helium, oxygen and iron nuclei at the level of observation have been estimated with help of the code CORSICA 6.616. The comparison show that the values of the function Xi**2 per one degree of freedom changes from 1.1 for iron nuclei to 0.9 for primary protons. As this difference is small all readings of detectors of the Vavilov-Cherenkov radiation have been used. At last, readings of underground detectors of muons with energies above 1 GeV have been exp…
In the near future the energy region above few hundreds of TeV may really be accessible for measurements of the atmospheric muon spectrum by the IceCube array. Therefore one expects that muon flux uncertainties above 50 TeV, related to a poor knowledge of charm production cross sections and insufficiently examined primary spectra and composition, will be diminished. We give predictions for the very high-energy muon spectrum at sea level, obtained with the three hadronic interaction models, taking into account also the muon contribution due to decays of the charmed hadrons.
