Reestimation of the energy of extensive air showers at the Yakutsk EAS array with the CORSIKA package

The responses of ground and underground muon scintillation detectors of the Yakutsk extensive air shower (EAS) array from primary particles with the energy E ₀ ≥ 10¹⁷ eV have been calculated within the QGSJET-01-d, QGSJET-II-04, SIBILL, and EPOS-LHC models with the CORSIKA package. A new estimate obtained for E ₀ is lower by a factor of about 1.41 than that previously obtained within the calorimetric method for EASs.     

New estimates of extensive-air-shower energies on the basis of signals in scintillation detectors

New formulas for estimating the energy of inclined extensive air showers (EASs) on the basis of signals in detectors by means of an original method and detailed tables of signals induced in scintillation detectors by photons, electrons, positrons, and muons and calculated with the aid of the GEANT4 code package were proposed in terms of the QGSJETII-04, EPOS LHC, and GHEISHA models. The parameters appearing in the proposed formulas were calculated by employing the CORSIKA code package. It is shown that, for showers of zenith angles in the range of 20?–45?, the standard constant-intensity-cut method, which is used to interpret data from the Yakutsk EAS array, overestimates the shower energy by a factor of 1.2 to 1.5. It is proposed to employ the calculated VEM (Vertical Equivalent Muon) signal units of 10.8 and 11.4 MeV for, respectively, ground-based and underground scintillation detectors and to take into account the dependence of signals on the azimuthal angle of the detector position and fluctuations in the development of showers.     

New Method for Estimating the Energy of Extensive Air Showers from Signals of Ground-Based Detectors of the Yakutsk Extensive Air Shower Array

A new method has been proposed for estimating the energy of inclined extensive air showers from signals of ground-based scintillation detectors of the Yakutsk extensive air shower array that are located at a distance of 600 m from the shower axis in the plane of the array and from the calculations of these signals within two hadron interaction models. New estimates of the energy have been obtained for 116 showers detected in different years. It has been shown that the energy spectra of particles of primary cosmic radiation measured at the Yakutsk array are in agreement with world data.     

Methods for estimating the energy of extensive air showers

A multilevel scheme for calculating estimates of the energy of extensive air showers on the basis of signals in different detectors is considered. The numerical energy estimates at specified values of signals in scintillation detectors are smaller than the experimental ones by a factor of about 1.6. The results of the calculation confirmed that the total flux of Cherenkov light is proportional to the shower energy. The flux of fluorescent light generated within 100 m from the shower core is due to only 60% of the total energy.     

A Method for Estimation of the Parameters of the Primary Particle of an Extensive Air Shower by a High-Altitude Detector

A method for estimation of the parameters of the primary particle of an extensive air shower (EAS) by a high-altitude detector complex is described. This method was developed as part of the Pamir-XXI project. The results may be useful for other high-altitude projects and the EAS method in general. The specific configurations of optical detectors for Cherenkov EAS radiation and charged-particle detectors, the methods for data processing, and the attainable accuracy of reconstruction of parameters of primary particles (energy, direction, mass/type) are presented. The results primarily cover optical detectors that are suitable for studying EASs from primary nuclei in the range of energies E⁰ = 100 TeV–100 PeV and showers from primary γ-quanta with energies of E_γ ≥ 30 TeV. Grids of charged-particle detectors designed to determine the EAS direction and energy in the E⁰ = 1 PeV–1 EeV range are also considered. The obtained accuracy estimates are the upper limits of the actual experimental accuracies.     

Radio signals from extensive air showers with the energies <Emphasis Type="Italic">E</Emphasis> <Subscript>0</Subscript> ≥ 10<Superscript>19</Superscript> eV according to data from the Yakutsk extensive air shower array

A radio instrument and results obtained from the measurements of the 32-MHz radio signal from particles of extensive air showers (EASs) with energies E₀ ≥ 1×10¹⁹ eV are reported in brief. The data were obtained at the Yakutsk EAS array in 1987–1989 (the first series of measurements) and in 2009–2014 (new series of measurements). The radio signal from EASs with energies above 10²⁰eV was detected at the Yakutsk EAS array for the first time, including the shower with the record energy of ~2×10²⁰ eV for the Yakutsk EAS array.     

Studying the muon and hadron components of extensive air showers with the Carpet-2 array

The method of separating muons and hadrons recorded by the Muon Detector of the Carpet-2 air shower array of Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) is described. The results of studying characteristics of the muon and hadron components of extensive air showers (EAS) with N _e ≥ 10⁵ are presented. For the range of distances 40–55 m from shower axes the numbers of hadrons with energies higher than 30 GeV and muons with energies above 1 GeV are obtained as functions of the shower size N _e .     

Spatio-temporal structure of the muon disk at <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 5 × 10<Superscript>16</Superscript> eV from Yakutsk EAS array data

We present the results of our study of the temporal structure of the muon disk at the Yakutsk array in extensive air showers with primary energies E₀ ≥ 5 × 10¹⁶ eV at distances of 250–1500 m from the shower axis obtained using a large muon detector with an area of 184 m² and a detection threshold of E_μ ≈ 0.5 sec θ GeV. We have found two components with different muon disk thicknesses that require significant revisions of our view of the development of extensive air showers.     

Heavy decaying dark matter and large-scale anisotropy of high-energy cosmic rays

We examine the role of the large-scale anisotropy of the high-energy cosmic ray distribution in a search for the heavy decaying dark matter (DM) signal. Using recent anisotropy measurements from the extensive air shower (EAS) observatories, we constrain the lifetime of the DM particles with masses 10⁷ ≤ M _X ≤ 10¹⁶ GeV. These constraints appear to be weaker than that obtained with the high-energy gamma-ray limits. We also estimate the desired precision level for the anisotropy measurements to discern the decaying DM signal marginally allowed by the gamma-ray limits and discuss the prospects of the DM search with the modern EAS facilities.     

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from Ground-Based Scintillation Detectors of the Yakutsk EAS Array

Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of E₀ ≥ 10¹⁷ 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 theQGSJET-01-d, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHCmodels by employing the CORSIKA code package. The new estimate of E₀ is substantially lower than its counterpart used earlier.     

Low-frequency radio emission induced by the coherent magneto-bremsstrahlung of charged particles of an extensive air shower

A previously unknown coherent low-frequency (0<ν<50 kHz) component of radio emission of an extensive air shower in the geomagnetic field is reported. This type of emission induces a high-intensity field (∼200 μV/m MHz at a distance of 100 km from the shower axis). This emission mechanism is believed to be responsible for the previously observed high-intensity radio emission of the shower at low frequencies. The possibility of radio detection of ultrahigh-energy (W ₀>10²¹ eV) cosmic rays is considered.     

Neutron “thunder” accompanying an extensive air shower

The role of the neutron component of extensive air showers at PeV and EeV energies is considered. The occurrence of neutrons delayed by several hundreds of microseconds with respect to the main shower front is explained by the production and slowing down of neutrons, mainly in the neutron monitor, when a PeV-EAS core falls on it, as well as in the nearby soil and environment. An important circumstance in study of EeV EASs is that neutrons form the dominant hadronic component at a distance of about 1 km from the EAS core and at delays about 5 μs with respect to the main shower front and may contribute to the signal of the detectors located at such distances.     

Radio emission of extensive air showers at microwave frequencies

It is found that the power of the incoherent radiation of ionization electrons of an extensive air shower in the frequency range of 150 GHz is more than 10^–24 W/m²Hz, with the shower energy ~10¹⁸ eV at a distance of 5 km from its axis. This means that, unlike fluorescent detectors, a radio telescope with an effective area of more than 300 m² can monitor the trajectory of showers with an energy higher than 10¹⁸ eV at any time of the day regardless of the weather. The spectrum maximum near the frequency of 150 GHz is roughly three orders of magnitude higher than the value experimentally measured in the characteristic band (~5-10 GHz).     

Spatiotemporal structure of pulses in detectors of Cherenkov light of extensive atmospheric showers

We calculated the pulses of the Cherenkov light of extensive atmospheric showers in Cherenkov radiation detectors at the Yakutsk array in the framework of the QGSJET-II model. It is shown that the calculated width of a pulse of Cherenkov light in a vertical proton-induced shower of energy of 10¹⁸–10²⁰ eV increases from 50 ns at a distance of 200 m from the shower axis to 700 ns at a distance of 1 km.     

Investigation of the structure of a muon disk for <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 5 × 10<Superscript>16</Superscript> eV according to data of the Yakutsk array for studying extensive air showers

The results are presented that were obtained at the Yakutsk array by investigating the time structure of a muon disk in extensive air showers of primary energy in the region E ₀ ≥ 5 × 10¹⁶ eV at distances of 250 to 1500 m from the shower core. The measurements were performed with a large muon detector that has an area of 184 m² and a detection threshold of E _μ≈0.5secθ GeV and which began operating in November 1995. Two components having different muon-disk thicknesses were discovered, and this requires strong modifications in the currently prevalent idea of the development of extensive air showers. The problem of the existence of E ₀ ≥ 10²⁰ eV events is considered. __________ Translated from Yadernaya Fizika, Vol. 68, No. 1, 2005, pp. 74–88. Original Russian Text Copyright ? 2005 by Glushkov, Dedenko, Sleptsov.     

Lateral distribution function of charged particles in EAS near the axis

High-precision measurements of the lateral distribution function (LDF) of charged particles near the axis of extensive air showers (EASes) were performed with the CARPET air shower array of the Baksan Neutrino Observatory for several ranges of N _e , including the knee region. For the sake of comparison with the experiment, calculations for primary protons and iron nuclei were made using the CORSIKA code (the QGSJET01C model of interaction). The measured experimental LDF is compared with our calculations.     

EMMA—a new underground cosmic-ray experiment

An experiment observing underground muons originating from cosmic-ray air showers is under preparation in the Pyhäsalmi mine, Finland. The aim is to cover an area of about 200–300 m², and the detector setup is capable of measuring the muon multiplicity and their lateral distribution. The detector is placed at a depth of about 85 m (corresponding about 240 m w.e.), which gives a threshold energy of muons of about 45 GeV. The detection of the multimuon events is motivated by partly unknown composition of the primary cosmic rays in the energy region of 10¹⁵–10¹⁶ eV, i.e., the knee region. In addition, by measuring only the higher energy muons of the air shower, the lowest energy muons being filtered out by the rock overburden, the data is sensitive also to the studies of the upper parts of the air shower. The experiment will be constructed mainly using drift chambers used previously in LEP detectors at CERN, but it can also be expanded using plastic scintillator detectors. The prototype detector is expected to be running in the beginning of 2006, and the full-size detector by the end of 2007.     

Estimation of the PCR mass composition in the energy range 1017–1019 eV on the basis of multicomponent analysis of the characteristics of EASs detected at the Yakutsk array

The characteristics of longitudinal and radial extensive air shower development derived from the results of detection of the charged particle flux and Cherenkov light in extensive air showers at the Yakutsk array. To estimate the primary cosmic ray composition, a combination of the parameters X_max and ρ₆₀₀ and the database simulated using the CORSIKA code (QGSJET model) for showers generated by five types of nuclei (p, He, C, Si, Fe) in the energy range 10¹⁷–10¹⁹ eV were used. Application of the multicomponent method made it possible to divide the showers into three groups (p + He), C, and (Si + Fe) and estimate their percentage. The error in identifying nuclei in the energy range 10¹⁷–10¹⁸ eV does not exceed 30%.     

Cosmic rays and supernova SN 1987a

Summary We discuss the possibility of obtaining information on the contribution to the galactic cosmic-ray flux by young pulsars searching for high-energy gamma-rays from SN 1987a. A small extensive air shower array operating in Chacaltaya (Bolivia, 5200 m a.s.l.) could give significant information at primary energiesE ₀∼10¹⁴ eV.     

Underground hadronic calorimeter for EAS studies

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