Cosmic ray primary mass composition above the knee: deduction from lateral distribution of electrons

Influence of shower fluctuations on the shape of lateral distribution of electrons in EAS of fixed size measured by scintillation counters is analyzed in framework of scaling formalism. Correction factors for the mean square radius of electrons are calculated for the experimental conditions of KASCADE array. Possible improvement of the primary mass discrimination by analysis of lateral distribution of EAS electrons is discussed in detail.Comment: Proceedings of the XIV International Symposium on Very High Energy Cosmic Ray Interaction

Spectra of hadrons and muons in the atmosphere: primary spectra, characteristics of hadron-air interactions

Self-consistency of interaction models QGSJET 01, SIBYLL 2.1, NEXUS 3.97 and QGSJET II is checked in terms of their ability to reproduce simultaneously experimental data on fluxes of muons and hadrons. From this point of view SIBYLL 2.1 gives the most acceptable, though not quite satisfactory, results. Analysis of the situation for muons supports our previous conclusions, that high-energy muon deficit is due both to underestimation of primary light nuclei fluxes in direct emulsion chamber experiments and to softness of $p+A\to\pi^\pm,K^\pm+X$ inclusive spectra in fragmentation region, especially prominent in case of QGSJET 01 model.Comment: Talk given at the XIVth ISVHECRI (Weihai, China, 2006

Anomalous diffusion of the cosmic rays in the fractal Galaxy

We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by galactic sources. The fractional diffusion equation proposed in our recent papers is used to describe the cosmic rays propagation in interstellar medium. We show that in the framework of this approach it is possible to explain the locally observed basic feature of the cosmic rays in the energy region 10¹⁰ ÷10²⁰ eV: distinction in spectral exponent of protons and other nuclei, mass composition variation, “knee” problem, flattering of the primary spectrum at E≥10¹⁸ ÷10¹⁹ eV

Recent results from Yakutsk experiment: development of EAS, energy spectrum and primary particle mass composition in the energy region of 10^15-10^19 eV

Experimental data obtained at the Yakutsk array after the modernization in 1993 are analyzed. The characteristics of EAS longitudinal and radial development found from the charged particle flux and EAS Cherenkov light registered at the Yakutsk complex array are presented. The energy spectrum of EAS obtained from Cherenkov light and an estimate of the PCR mass composition are presented.Comment: 10 pages, 11 figures. Invited talk on XIV ISVHECRI; to be published in Nucl. Phys. B (Proc. Supply

Spectra of cosmic ray electrons and positrons in the Galaxy

A new study of the cosmic ray electron and positron spectra is presented, using an anomalous diffusion model to describe the particles propagation in the Galaxy. The parameters defining the anomalous diffusion have been recently determined from the study of nuclei propagation. The computed electron and positron spectra under assumption that positrons, as well as electrons, are accelerated by a galactic source, are in a good agreement with the measurements. The source spectral index, found from experimental data, in this approach turns out to be equal to 2.95 for electrons and positrons. The predicted positron fraction e⁺/(e⁺+e⁻) in high energy region E≈10² ÷10³ GeV is ~0.06

Properties of the Interstellar Medium and the Propagation of Cosmic Rays in the Galaxy

The problem of the origin of cosmic rays in the shocks produced by supernova explosions at energies below the so called 'knee' (at ~3*10$^6$ GeV) in the energy spectrum is addressed, with special attention to the propagation of the particles through the inhomogenious interstellar medium and the need to explain recent anisotropy results, [1]. It is shown that the fractal character of the matter density and magnetic field distribution leads to the likelihood of a substantial increase of spatial fluctuations in the cosmic ray energy spectra. While the spatial distribution of cosmic rays in the vicinity of their sources (eg. inside the Galactic disk) does not depend much on the character of propagation and is largely determined by the distribution of their sources, the distribution at large distances from the Galactic disk depends strongly on the character of the propagation. In particular, the fractal character of the ISM leads to what is known as 'anomalous diffusion' and such diffusion helps us to understand the formation of Cosmic Ray Halo. Anomalous diffusion allows an explanation of the recent important result from the Chacaltaya extensive air shower experiment [1], viz. a Galactic Plane Enhancement of cosmic ray intensity in the Outer Galaxy, which is otherwise absent for the case of the so-called 'normal' diffusion. All these effects are for just one reason: anomalous diffusion emphasizes the role of local phenomena in the formation of cosmic ray characteristics in our Galaxy and elsewhere.Comment: 18 pages, 5 figures, accepted by Astropartoicle Physic

Air Shower Simulations in a Hybrid Approach using Cascade Equations

A new hybrid approach to air shower simulations is described. At highest energies, each particle is followed individually using the traditional Monte Carlo method; this initializes a system of cascade equations which are applicable for energies such that the shower is one-dimensional. The cascade equations are solved numerically down to energies at which lateral spreading becomes significant, then their output serves as a source function for a 3-dimensional Monte Carlo simulation of the final stage of the shower. This simulation procedure reproduces the natural fluctuations in the initial stages of the shower, gives accurate lateral distribution functions, and provides detailed information about all low energy particles on an event-by-event basis. It is quite efficient in computation time.Comment: 19 Pages, 10 Figures accepted version with more explanations about source functions, in print PR

The spectrum features of UHECRs below and surrounding GZK

The energy spectrum of UHECRs is discussed on the basis of the Yakutsk array database analysis. In the region E=0.1 to 30 EeV the showers are detected under trigger-500, while at energies above 30 EeV the whole acceptance area for trigger-1000 is used in order to utilize all the data available in the region of GZK cutoff.Comment: Invited talk at CRIS2004: GZK and surroundings, Catania, Italy, 31.05.04. To appear in Nucl. Phys. B Proc. Supp