Pulsars as the most probable sources of ultrahigh-energy cosmic rays

The arrival directions of ultrahigh-energy extensive air showers detected at the Yakutsk extensive air shower array are considered. The maxima revealed in the distribution of the arrival directions of showers and doublets are found to correlate with the coordinates of pulsars located in the Galactic plane. It is shown that the three showers detected at the Yakutsk extensive air shower with the highest energies E > 10²⁰ eV correlate with the nearest pulsars.     

Landau-pomeranchuk-migdal air showers initiated by ultra-high-energy neutrinos and their detection in a satellite-based experiment

The ultra-high-energy (UHE) atmospheric showers with strong influence of the Landau-Pomeranchuk-Migdal (LPM) effect (here after LPM showers) are exclusively expected to be produced by UHE neutrinos. Studies on the characteristics of the LPM showers are essentially important to discriminate neutrino shower (which produced by neutrino interaction) from hadronic shower (initiated by primary hadron). We calculate the LPM showers initiated by electrons with energies of 10¹⁸ to 10²¹ eV, using the hybrid method as exactly as possible. Reflecting the change in the air density along the shower trajectories, the variety of the LPM-shower profiles is shown in different cases for their starting points in atmosphere. Through the study of time profiles of air fluorescent photon components from the LPM showers, the detection capability of UHE neutrinos has also been investigated by the satellite-based experiment with a large acceptance, e.g., the TUS experiment.     

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.     

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 .     

Electrons and muons in extensive air showers of energies E 0≥3×1017 eV: Yakutsk array data and QGSJET model

The results obtained from an analysis of the 1974–1998 Yakutsk array data on muons with threshold energy E _μ ≈ 1.0 × secθ GeV and on all charged particles (electrons and muons) in extensive air showers (EAS) are reported and compared with the results of calculations based on the model of quark-gluon strings with jets. For energies of E ₀≤3×10¹⁸ eV and zenith angles of θ≤45°, the results of the model calculations are consistent with the measured properties of the showers, while, for higher energy EASs, there are considerable discrepancies, which are probably due to the change in the development of the shower cascade in the region E ₀≥3×10¹⁸ eV.     

Test of Lorentz invariance through observation of the longitudinal development of ultrahigh-energy extensive air showers

An idea that Lorentz invariance can be violated was proposed by Coleman and Glashow to overcome the astrophysical problems of air showers of ultrahigh energies E>10²⁰ eV. This statement can be tested by analyzing experimental data on these showers. The longitudinal development of showers and the distribution of the depths of shower maxima were calculated in the model of quark-gluon strings with allowance made for the Landau-Pomeranchuk-Migdal effect and the interactions of ultrahigh-energy neutral pions. Comparison of the calculations with available experimental data provides a new bound |c _γ?c _π°| <0^?20 for the possible difference between the speeds of photons and neutral pions. This bound becomes |c _γ?c _π°|<10^?22 when one takes the upper limiting value for the observed depth of maximum.     

Muons in extensive air showers of energies E 0=1016.6–1019.8 eV

Data on muons with the threshold energy E _μ≈1.0×secθ GeV in extensive air showers of energies E ₀≥4×10¹⁶ eV measured on the Yakutsk and Akeno arrays are jointly analyzed. The results are compared with the calculations by the quark-gluon-string model with jets. It is shown that this model does not contradict the data measured for energies E ₀≤10¹⁸ eV on both arrays under the assumption that the primary particle composition differs from the composition where heavy nuclei dominate over protons. Experimental data for energies E ₀≥3×10¹⁸ eV indicate that the shower development differs from that predicted by the quark-gluon-string model with jets.     

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.     

Spatial distribution of Čerenkov light from extensive air showers

The spatial distribution function of Čerenkov radiation from particles of extensive air showers with energies in the interval 10¹²–10¹⁷ eV calculated by the computer code CORSIKA and the approximation constructed on the basis of this calculation have allowed us to reconstruct the events, that is, to reconstruct the type and energy of the particle that generated extensive air shower from signal amplitudes of Čerenkov light registered with the Tunka-25 facility. The calculated spatial distribution function of Čerenkov light is in good agreement with the fitting function constructed in [1–4] to reconstruct the parameters of extensive air showers registered with the Tunka-25 facility. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 43–48, July, 2006.     

On the sensitivity of the spatial-angular distribution of the Cherenkov light in extensive air showers to the mass composition of primary cosmic rays with energies of 10<Superscript>15</Superscript>–10<Superscript>16</Superscript> eV

This paper analyses the possibility of separating distinct groups of nuclei of primary cosmic rays with energies of 10¹⁵–10¹⁶ eV from the data on the spatial-angular distribution of Cherenkov light in extensive air showers. The paper shows that using an array of a few (3–4) telescopes with a moderately sized angular cell ∼0.5° placed at a distance ∼100 m from one another, one can achieve almost complete separation of the showers initiated by these nuclei (the Bayesian classification error is a few percentage points for the case of separating primary protons and nitrogen nuclei). The authors propose new parameters of the angular Cherenkov image that can greatly enhance the separability of the shower classes as compared to the approach based on the traditional parameters.     

STAR CLUSTER: a tracking array for gamma-ray astronomy

Summary A new type of extensive air shower array-telescope is being constructed, close to the GREX scintillator array at Haverah Park. The design of the new instrument is based on identification and measurement of individual shower particles by means of pattern recognition techniques applied to data from LST chambers above and below a thin sheet of high-Z material. Air showers will be detected in the range from 10¹⁴ eV to 10¹⁸ eV. The directions of the shower primaries will be reconstructed with an accuracy of a few tenths of a degree using triangulation between tracks of detected shower particles: >1 GeV electrons, photons and muons. Particle densities measured at the detector locations will be used to calculate shower sizes and core locations. Information about the height of production of the high-energy secondaries will be obtained for each shower. This information will be taken into account in calculating the primary energies. It will be used together with the observed muon content (ratio of muons to all particles), to draw conclusions about the nature of the primary particles. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Zur longitudinalen Verteilung der Elektronen in großen Luftschauern

The standard deviationσ of the instantaneous distribution of electrons in extensive air showers at sea level has been measured by coincidence of two spark counters, a cloud chamber providing data on arrival directions and particle densities. The values published up to now were in the range 2<σ<8 ns and the standard time deviationσ ₀ due to instrumental fluctuations was about 4 ns. In this experiment with aσ ₀=1,8 ns mean delaysσ have been obtained between 1 and 2 ns, the values decreasing with increasing particle density. This tendency may be due to the fact that the mean separations of the electrons, taken perpendicular to the shower front, are increasing with distance from the shower axis. The fractional contribution of showers within a given range of sizes, the axes of which came down within a given interval of distances from the counters has been calculated. It was concluded that 80% of the showers triggering the two counters were in the range from 10⁵ to 10⁷ particles. By means of these calculations, using the measured values for the mean delaysσ at different particle densities, a simple curve has been constructed which gives the mean separations of electrons vs distance from the shower axis up to 1000 m and is in good agreement with the experimental data ofLinsley andScarsi for great distances from the shower axis.     

Possible observations of new physics in ultrahigh-energy cosmic rays

The muon lateral structure functions in giant air showers induced by primary photons have been simulated with the help of original codes. Particularly, the densities of muons with energies above 0.5 and 1 GeV at a distance of 1000 m from the shower core have been estimated for gamma-induced showers of various energies. A comparison with the results of calculations for hadronic showers shows a considerable deficit of muons in the gamma-induced showers. The density of muons at a distance of 1000 m from the shower core happened to be ≳ 10 times larger for the hadronic showers. Some possible constraints of the source models with superheavy-dark-matter particles and topological defects are discussed. The text was submitted by the authors in English.     

Identification of the primary cosmic ray

The nature of the primary particle giving rise to an atmospheric shower may be, to some extent, inferred from the observable properties: longitudinal profile (especially position of the maximum of the number of charged particles) or shape at ground level (lateral distribution, curvature and thickness of the shower front, muonic component). Distinguishing different nuclei cannot be performed unambiguously on a single shower, because of the random fluctuations in the first steps of the cascade; however, it is possible to study the composition of the incident flux on a statistical basis: showers from heavier nuclei have a faster development, and contain more muons. The uncertainties on the hadronic interactions at the highest energies limit the reliability of the identification. Other primaries, if they exist, could be easier to distinguish. Photons would give a slower development than protons, especially at highest energies, and a very reduced muonic component; neutrinos would be characterized by deep interactions in the atmosphere, or even within the Earth, giving almost horizontal showers with a large electromagnetic component, clearly different from the muonic tail of showers induced in the upper atmosphere by nuclei. Such ‘exotic’ primaries have not yet been observed. To cite this article: P. Billoir, P. Sommers, C. R. Physique 5 (2004).     

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.     

Study on the structure functions of electrons and the energy flow in the soft component of cosmic-ray extensive air showers

Summary Cosmic-ray air shower structure functions for the distance dependence of electron density in cosmic-ray air showers in the size range 10⁴⋎10⁸ have been computed for their intercomparison and comparison with Monte Carlo simulation results and measurements from recent experiments. The analysis has yielded the present status of theoretical structure functionsvis à vis experimental results and Monte Carlo simulation distributions. The effect of core location error on the lateral distribution of electrons is also discussed from the point of view of different theoretical and experimental results. The energy flow in the soft component of air showers of size ∼4·10⁵ has been evaluated within a ring of radius 10m about the axis of the showers.     

New energy estimates of extensive air showers using signals detected at great distances from the shower axis

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 _θ 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.     

Mass Composition of Cosmic Rays with Energies above 1017 eV According to the Data from the Muon Detectors of the Yakutsk EAS Array

The lateral distribution of muons in extensive air showers with energies above 1017 eV detected by underground scintillation detectors with a threshold of 1.0 GeV at the Yakutsk array in 1986–2016 has been analyzed. The experimental data on the muon flux density at a distance of 300 m from the shower axis have been compared to the calculations within various models of hadron interactions at ultrahigh energies. The experimental data are in the best agreement with the QGSJet01 and QGSJet II-04 models. The mass composition of cosmic rays in the energy range of (1–30) × 10¹⁷ eV changes from middle nuclei to a purely proton composition.

     

The Renaissance of Radio Detection of Cosmic Rays

Nearly 50 years ago, the first radio signals from cosmic ray air showers were detected. After many successful studies, however, research ceased not even 10 years later. Only a decade ago, the field was revived with the application of powerful digital signal processing techniques. Since then, the detection technique has matured, and we are now in a phase of transition from small-scale experiments accessing energies below 10 ¹⁸ eV to experiments with a reach for energies beyond 10 ¹⁹ eV. We have demonstrated that air shower radio signals carry information on both the energy and the mass of the primary particle, and current experiments are in the process of quantifying the precision with which this information can be accessed. All of this rests on solid understanding of the radio emission processes which can be interpreted as a coherent superposition of geomagnetic emission, Askaryan charge-excess radiation, and Cherenkov-like coherence effects arising in the density gradient of the atmosphere. In this article, I highlight the “state of the art” of radio detection of cosmic rays and briefly discuss its perspectives for the next few years.     

平均能量为2×1015eV的宇宙线入射方向研究

从1982年5月到1983年1月,悉尼大学的小型宇宙线观测阵列记录了多于17,000个能量为6×10¹⁴—5×10¹⁶eV的宇宙线广延大气簇射事例。使用谐波分析和X²检验法,对这些宇宙线的入射方向进行了研究,没有发现有意义的各向不同性。 关键词：