Investigation of primary cosmic rays at the Moon’s surface

The possibility of experimentally studying primary cosmic rays at the Moon’s surface is considered. A mathematical simulations of showers initiated in the lunar regolith by high-energy particles of primary cosmic rays is performed. It is shown that such particles can in principle be recorded by simultaneously detecting three components of backscattered radiation (secondary neutrons, gamma rays, and radio emission).     

Depth of the maximum of extensive air showers and mass composition of primary cosmic radiation at an energy of 4 × 10<Superscript>17</Superscript> eV according to data on radioemission from extensive air showers

The results of a reanalysis of experimental data on extensive-air-shower radioemission that were obtained previously at the Moscow State University array for studying extensive air showers are presented. The lateral distribution of radioemission is given for showers characterized by a primary energy of 4 × 10¹⁷ eV and a zenith angle of θ = 35°. On the basis of an analysis of a lateral distribution of radioemission, the average value of the shower-maximum depth at a primary energy of 4 × 10¹⁷ eV is estimated at X _max = 655 ± 13 g/cm². Estimates of themass content of primary radiation that were obtained from an analysis of the distribution of X _max are compatible with the hypothesis that the role of light nuclei becomes more pronounced at energies above 10¹⁷ eV.     

Study of primary cosmic rays on the Moon’s surface and in orbit around the Moon

A mathematical model for experiments aimed at studying the primary cosmic rays on the Moon’s surface and in orbit around the Moon is considered. The feasibility of simultaneously registering in three components (secondary neutrons, gamma rays, and radio emission) particles of primary cosmic rays via reverse current in showers developing in the lunar regolith is demonstrated.     

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.     

Energy spectra of secondary particles in γ families and their sensitivity to the spectrum of primary cosmic rays

Spectra of secondary particles (γ-rays) in γ-families detected in the X-ray chambers in the Pamirs (H = 600 g cm^?2) have been analyzed. These γ-ray spectra show a bend at the energy E* _γ ≈ (ΣE _γ )^min, where (ΣE _γ )^min is the lowest total energy of γ-rays in the families above which γ-families were selected. The bend is not related to the knee in the spectrum of primary particles; it is due to the use of the ΣE _γ selection criterion. The E _γ spectrum slope is sensitive to the spectrum of the primary cosmic rays in the region E _γ ≥ (ΣE _γ )^min.     

Spatial-frequency characteristics of radio emission induced by interaction of an extensive air shower with the Earth’s surface

The spatial directional pattern of the radio emission induced by interaction of the excess electrons of an extensive air shower with the Earth’s surface was found in the approximation of perfect soil conductance. The results made it possible to determine the frequency range (≈0.2–1 MHz), within which the radio emission of the shower is maximum, provided that this emission mechanism is valid. In addition, it became possible to explain the previously observed lack of direct proportionality between the shower energy and the radio signal amplitude. It was found that this disproportionality is caused mainly by the high directivity of low-frequency (0.2–3 MHz) radiation patterns within a wide range of the values of the axial tilt.     

Ordered structure of the directions of arrival of E<Subscript>0</Subscript>∼5×10<Superscript>17</Superscript> eV cosmic rays according to data from the Yakutsk array for recording extensive air showers

Results are presented that were obtained by analyzing arrival directions for cosmic rays recorded by the Yakutsk array between 1974 and 2001 in the energy range E₀=10^17.6–17.9 eV for zenith angles in the region θ≤53°. It is shown that their flux consists of two components—an isotropic (about 75%) and a cluster (about 25%) one—that are characterized by sharply different degrees of anisotropy. At E₀=10^17.7–17.8 eV, the observed showers are found to be strongly correlated with the Supergalaxy plane.     

Variation in the energy spectra of primary cosmic rays for 2007–2015, according to data from the URAGAN muon hodoscope

Simulations of how secondary components of cosmic rays are generated and pass through the atmosphere are performed using the CORSIKA software package. The relationship between the vertical projection of the local anisotropy vector A _Z and the index of primary particle spectrum γ is calculated. The time series of A _Z for 2007–2015 are obtained using data from the URAGAN muon hodoscope. Matrix data corrected for barometric and temperature effects are used to estimate A _Z . Using the A _Z time series, the average annual daily variations Δγ are estimated. Annual and daily variations in the slope of the energy spectrum of primary protons are observed.     

Multipolar anisotropy of <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ⩾ 10<Superscript>17</Superscript> eV cosmic rays according to data of the Yakutsk array for studying extensive air showers

The results obtained by analyzing arrival directions for primary cosmic particles characterized by energies in the region E ₀ ⩾ 10¹⁷ eV and zenith angles in the range θ ⩽ 60° and detected at the Yakutsk array for studying extensive air showers (EASs) over the period spanning 1974 and 2009 are presented. It is shown that these events exhibit different anisotropies in different energy intervals.     

On the origin of <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 10<Superscript>17</Superscript> eV cosmic rays according to data from the Yakutsk array for studying extensive air showers

Results are presented that were obtained by analyzing the energy spectrum and anisotropy of E ₀ ≥ 10¹⁷ eV primary cosmic rays on the basis of data accumulated at the Yakutsk array for studying extensive air showers over the period between 1974 and 2004. It is shown that spectra corresponding to different regions of the sky differ in shape. Particle fluxes going from the Galaxy and Supergalaxy (a local supercluster of galaxies) disks are enhanced for E ₀ ≥ 5 × 10¹⁸ eV and are reduced for E ₀ ≤ (2–3) × 10¹⁸ eV. This observation is interpreted as a manifestation of the possible interaction between extragalactic primary cosmic rays and matter of the above structures of space.     

Small-scale anisotropy and composition of <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≈ 10<Superscript>17</Superscript> eV cosmic rays according to data from the Yakutsk array for studying extensive air showers

Results are presented that were obtained from an analysis of arrival directions for cosmic rays of energy in the range E ₀ ≈ 10^16.9–17.2 eV that were recorded by the Yakutsk array between 1974 and 2001 at zenith angles of θ ≤ 45°. It is shown that a considerable part of them form clusters that have small-scale cellular structure. In all probability, these showers are generated by neutral particles of an extragalactic origin.     

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.     

Collection of materials presented at the conference “Geometry and Operator Theory” dedicated to N. Teleman’s 65th birthday celebration, Ancona, 20–22 September 2007

This paper precludes the proceedings of the conference “Geometry and Operator Theory” dedicated to N. Teleman’s 65th birthday celebration (Ancona, September 2007)