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The main problems of superhigh energy cosmic ray physics are discussed. It is pointed out that the existing EAS arrays can not improve the level of experimental research in the near future and the arrays of a new generation are very much needed. The short description of the constructed EAS-1000 array and its first stage EAS-100 is given.

Experimental muon number distributions in EAS obtained at Moscow State University are analysed to estimate the primary mass composition at energies before and after knee. The mass composition before the knee corresponds to the normal one (as at E 0 ∼10 12 eV), while experimental data after the knee are in agreement with the assumption that normal composition becomes enriched slowly by heavy nuclei, as also supported by contemporary diffusion models.

The TAIGA project is aimed at solving the fundamental problems of gamma-ray astronomy and physics of ultrahigh energy cosmic rays with the help of the complex of detectors, located in the Tunka valley (Siberia, Russia). TAIGA includes a wide-angle large area Tunka-HiSCORE array, designed to detect gamma-rays of ultrahigh energies in the range 20 - 1000 TeV and charged cosmic rays with energies of 100 TeV - 100 PeV, large area muon detector to improve the rejection of background EAS protons and nuclei and a network of imaging atmospheric Cherenkov telescopes for gamma radiation detection. We discuss the goals and objectives of the complex features of each detector and the results obtained in the first stage of the HiSCORE installation.

Data obtained with two detectors located at the Tunka Cosmic Ray facility are presented. The Cherenkov light array for registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons since 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 · 10 15 −10 18 eV measured for 1540 hours of observation are presented.The preliminary all particle energy spectrum by the data of Tunka-HiSCORE prototype array, installed in 2013, is presented. Some additional experiments in the Tunka Valley are briefly described.

The origin of ultra-high-energy cosmic rays (UHECRs) is one of the most intriguing problems of modern cosmic ray physics. We briefly review the main astrophysical models of their origin and the forthcoming orbital experiments TUS and JEM-EUSO, and discuss how the new data can help one solve the long-standing puzzle., 4 pages; prepared for ECRS-2012 (http://ecrs2012.sinp.msu.ru/); v2: a reference added

The HiSCORE (Hundred Square km Cosmic ORigin Explorer) project is a ground-based large-area wideangle air shower detector array that will measure gamma rays and cosmic rays in the energy range of 10 TeV up to 1EeV. Each detector array station consists of four separate light collectors with an 8-inch photomultiplier (PMT) at each end. The first station prototype has already been deployed to Tunka valley. On-site station integration and first measurements have been made. This poster will focus on the hardware aspects and the first light results of the single station.

Experimental muon number distributions in Extensive Air Showers obtained at Moscow State University with enlarged statistics and improved procedure for muon number determination are analysed in the framework of an updated quark-gluon string model. The primary mass composition at energies before and after the kink in the primary energy spectrum is estimated. Mass composition before the kink is close to a normal one, and after the kink experimental data agree with the assumption that normal composition becomes enriched slowly by heavy nuclei according to the Peters-Zatsepin model.

A new array for studying ultra-high energy cosmic rays was inaugurated in 2009 in the Tunka Valley, about 50 km from Lake Baikal. Having an area of 1 km2, the new facility allows us to study cosmic rays with energies of 1015–1018 eV via the a unified method for registering Cherenkov radiation from extensive air showers (EASes) and is making a substantial contribution to understanding the origin of ultra-high energy cosmic rays. We describe the current state of the experiment, the new methodological approach, our initial results, and the plans for further development of the array.

A new 1 km2 EAS Cherenkov detector in the Tunka Valley has been put into full operation in the fall of 2009. In this paper we give a short description of the detector and discuss its physics capabilities.

Angular distributions of extensive air showers with different number of charged particles in the range 2.5x10^5--4x10^7 are derived using the experimental data obtained with the EAS MSU array. Possible approximations of the obtained distributions with different empiric functions available in literature, are analysed. It is shown that the exponential function provides the best approximation of the angular distributions in the sense of the chi-squared criterion., 5 pages including 1 figure

The differencies in the underlying assumptions of hadronic interaction models are analysed. The influence of assumed momentum distributions of quarks (antiquarks), positioned at the ends of quark-gluon strings, is investigated in the framework of QGSJET model. It is shown that for the choice of the effective exponent of these distributions α q → 1 calculated EAS characteristics become nearer to the predictions of SYBILL model.

The new EAS Cherenkov array TUNKA-133, with about 1 km**2 sensitive area, is being installed in the Tunka Valley. The investigated energy range is 10**15-10**18 eV. It will consist of 133 optical detectors based on EMI9350 PMTs. Optical detectors are grouped into 19 clusters with 7 detectors each. The detectors are connected to the cluster box with RG-58 cables. Every PMT signal is digitized in the cluster box with 200 MHz FADC. The cluster boxes are connected to the data acquisition center with a 1 Gb/s optical link. A detailed description of the data acquisition system (DAQ) is presented., 5 pages, 4 figures, Proceedings of the 10th ICATPP Conference,Como Italy, 8-12 October 2007

The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 · 10 15 -10 18 eV measured for 1540 hours of observation are presented.

The propagation of high-energy cosmic rays in the Galaxy is investigated. Solutions of a diffusion model are combined with numerically calculated trajectories of particles. The resulting escape path length and interaction path length are presented and energy spectra obtained at Earth are discussed. It is shown that the energy spectra for heavy elements should be flatter as compared to light ones due to nuclear interactions during the propagation process. The obtained propagation properties of ultra-heavy elements indicate that these elements could play an important role for the explanation of the second knee in the cosmic-ray energy spectrum around 400 PeV., Comment: 13 pages, 8 figures, Astroparticle Physics in press

An efficient scheme for one-dimensional extensive air shower simulation and its implementation in the program conex are presented. Explicit Monte Carlo simulation of the high-energy part of hadronic and electro-magnetic cascades in the atmosphere is combined with a numeric solution of cascade equations for smaller energy sub-showers to obtain accurate shower predictions. The developed scheme allows us to calculate not only observables related to the number of particles (shower size) but also ionization energy deposit profiles which are needed for the interpretation of data of experiments employing the fluorescence light technique. We discuss in detail the basic algorithms developed and illustrate the power of the method. It is shown that Monte Carlo, numerical, and hybrid air shower calculations give consistent results which agree very well with those obtained within the corsika program.

Two structures in the all-particle energy spectrum of cosmic rays, the knee at 4 PeV and the second knee around 400 PeV are proposed to be explained by a phenomenological model, the poly gonato model, connecting direct and indirect measurements. Within this approach the knee is caused by a successive cut-off of the flux for individual elements starting with protons at 4.5 PeV. The second knee is interpreted as the end of the stable nuclei of the periodic table. To check some key features of this model calculations of the cosmic ray energy spectrum and the propagation path length at energies from 10^14 to 10^19 eV have been performed within the framework of a combined approach based on the diffusion model of cosmic rays and a direct simulation of charged-particle trajectories in the Galaxy., Comment: Invited talk, presented at the "Workshop on Physics of the End of the Galactic Cosmic Ray Spectrum", Aspen, USA, April 25 - 29, 2005

The project of an EAS Cherenkov array in the Tunka valley/Siberia with an area of about 1 km^2 is presented. The new array will have a ten times bigger area than the existing Tunka-25 array and will permit a detailed study of the cosmic ray energy spectrum and the mass composition in the energy range from 10^15 to 10^18 eV., Comment: 3 pages, 2 figures, to be published in IJMPA

We give a general introduction to high‐energy cosmic ray physics before discussing somewhat more in detail new results concerning solutions of the cascade equations for the air shower evolution.

TAIGA stands for ``Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy'' and is a project to built a complex, hybrid detector system for ground-based gamma-ray astronomy from a few TeV to several PeV, and for cosmic ray studies from 100 TeV to 1 EeV. TAIGA will search for ``PeVatrons'' (ultra-high energy gamma-ray sources) and measure the composition and spectrum of cosmic rays in the knee region (100 TeV–10 PeV) with good energy resolution and high statistics. TAIGA will include Tunka-HiSCORE — an array of wide-angle air Cherenkov stations, an array of Imaging Atmospheric Cherenkov Telescopes, an array of particle detectors, both on the surface and underground and the TUNKA-133 air Cherenkov array.

The purpose of this paper is twofold: first we want to introduce a new type of hadronic interaction model (NEXUS), which has a much more solid theoretical basis as, for example, presently used models like QGSJET and VENUS, and ensures therefore a much more reliable extrapolation towards high energies. Secondly, we want to promote an extensive air shower (EAS) calculation scheme, based on cascade equations rather than explicit Monte Carlo simulations, which is very accurate in calculations of main EAS characteristics and extremely fast concerning computing time. We employ the NEXUS model to provide the necessary data on particle production in hadron-air collisions and present the average EAS characteristics for energies 10^14 - 10^17 eV. The experimental data of the casa-blanka group are analyzed in the framework of the new model., Comment: 15 pages, 8 figures

The radio emission from extensive air showers with energies up to 1017 eV has been calculated. The calculated lateral distribution of the radio emission is in good agreement with the LOPES-10 experimental data.

Distribution of maximum depths of extensive air showers (EAS) with energies of 1017–1018 eV is restored from the lateral distribution of EAS radio emission measured by the LOPES experiment (40-80 MHz). Dependence of the EAS maximum depth on its energy is constructed and mass composition of cosmic rays is estimated. It follows from the obtained dependencies that the fraction of light cosmic ray's nuclei increases in the energy range under consideration.

Using the data of the EAS MSU array and model calculations we have performed the search of events with abnormally small fraction of muons with energy above 10 GeV in showers with particle numbers greater than 2.107 and with zenith angles less than 30 degrees. The aim of the work – to estimate a fraction of muon-poor showers in which the underground muon detector registered no muons. These events may be identified as showers generated by primary gamma-quanta of ultrahigh energies. With good statistical accuracy we have confirmed our earlier conclusion that the content of gamma-quanta in the primary cosmic ray flux may be as much as 2 % at energies about 1017 eV.

With the HiSCORE (Hundred*i Square kilometer Cosmic ORigin Explorer) experiment we aim at the exploration of the accelerator sky using indirect air shower observations of cosmic rays from 100 TeV to 1 EeV and gamma rays above 10 TeV to several PeV. In this paper the HiSCORE detector is discribed and the results of the first prototype deployment are shown. Several components are discussed like the photomultiplier tubes, the clip-sum-trigger and the DRS4 based data acquisition. We present data taken with a first prototype station in April 2012 at Tunka.

The lateral distribution function (LDF) of radio emission from an extensive air shower is considered as the basic signature sensitive to the shower longitudinal development and, as a consequence, to the mass of a primary cosmic ray's particle that initiated a given shower. The peculiarities in the LDF's structure as well as their sensitivity to the height of shower maximum are investigated and explained.

We present spectra and mass composition of cosmic rays incoming to the Earth in the energy range (0.5-2)10^20 eV. As their sources we consider Seyfert galaxies located at distances < 40 Mpc, following an acceleration model for such moderate-power objects. Mass composition of the particles at sources is assumed to be mixed. Generation spectra are described by a function E^(-g0), where g0 is an arbitrary parameter. It is shown that the assumptions adopted make it possible to describe experimental data provided by HiRes and Pierre Auger Observatory, using different values of g0., 16 pages, 10 figures

The status of EAS:-1000 array is presented. Considering the possibility of data acquisition on EAS muons and Cherenkov light the problem of CR mass composition investigations is discussed.

It is shown that, when the scaling in hadron interactions is valid at energies of about 2 x 10'*eV for x = 0.1-1.0 accurate within loo/& the extrapolation of the 'scaling model' to the super-high-energy range 1015-10'7 eV contradicts the experimental data on extensive air showers (EAS).

The results of the experimental study of the burst spectrum in ionization chambers underground accompanied by EAS are presented. The investigations were carried out at depths of 20 and 40 m.w.e. The absence of absorption of the burst intensity with increasing depth underground (from 20 to 40 m.w.e.) and the form of the burst spectrum make it possible to affirm that the bursts in EAS underground are generated by high-energy muons. The experiment shows that the 10–103 GeV EAS muon energy spectrum has an exponent γ = 1.2–1.5.