A. G. Bogdanov

Investigation of the properties of the flux and interaction of ultrahigh-energy cosmic rays by the method of local-muon-density spectra

A new method for studying extensive air showers is considered. The method is based on the phenomenology of the localmuon density. It is shown that measurement ofmuon-density spectra at various zenith angles makes it possible to obtain information about the energy spectrum, mass composition, and interaction of cosmic rays over a broad range of energies (1015–1018 eV) by using a single array of comparatively small size. The results obtained from a comparison of experimental data on muon bundles from the DECOR coordinate detector with the results of simulation performed under various assumptions on the properties of the primary flux and for various hadron-interaction models are presented, and possible versions of the interpretation of these results are discussed.

Ultra-high energy cosmic ray investigations by means of EAS muon density measurements

A new approach to investigations of ultra-high energy cosmic rays based on the ground-level measurements of the spectra of local density of EAS muons at various zenith angles is considered. Basic features of the local muon density phenomenology are illustrated using a simple semi-analytical model. It is shown that muon density spectra are sensitive to the spectrum slope, primary composition, and to the features of hadronic interaction. New experimental data on muon bundles at zenith angles from 30° to horizon obtained with the coordinate detector DECOR are compared with CORSIKA-based simulations. It is found that measurements of muon density spectra in inclined EAS give possibility to study characteristics of primary cosmic ray flux in a very wide energy range from 10 15 to 10 19 eV.

Energy spectrum of cascade showers generated in water by near-horizontal muons

We discuss measuring cascade shower energy using the NEVOD Cherenkov water detector with a spatial lattice of quasi-spherical modules (QSMs). Dense QSM spacing makes it possible to reconstruct a number of cascade particles along the shower axis from the PMT response amplitude. Our cascade curve reconstruction technique is applied to showers generated by near-horizontal high-energy muons selected using the DECOR coordinate detector deployed around NEVOD. The first results from cascade energy spectrum measurements are reported.

NEVOD-DECOR experiment: results and future

Russian-Italian NEVOD-DECOR experiment on the measurements of the local muon density spectra (LMDS) at various zenith angles gave possibility to obtain information on primary cosmic ray flux and interaction characteristics in a record wide energy range from 1015 to more than 1018 eV. Comparison of the measurement results with CORSIKA-based simulations showed the increase of LMDS slope at PeV energies of primaries (corresponding to the first knee); a trend to a heavier primary mass composition above the knee; indication for a second knee (a further increase of the spectrum slope near 1017 eV). At large zenith angles and high muon densities (corresponding to primary energies around 1018 eV) a considerable excess of muon bundle events in comparison with the expectation based on independent estimates of the primary spectrum and widely used hadron interaction models has been found. In 2011, a new phase of measurements of the energy spectrum of cascade showers initiated by high-energy muons in water and of the energy deposit of muon bundles at various zenith angles and muon multiplicities started. Further plans include the deployment of a traditional EAS array around the NEVOD-DECOR complex.

Measuring the spectrum of the local density of charged particles on the SCT setup

The first results from measuring spectra of the local density of charged particles in extensive air showers in the energy range of ∼1014–1015 eV on the SCT setup (part of the NEVOD experimental complex), obtained using two independent methods, are presented. Experimental data are compared to calculations performed using the CORSIKA program.

A proposed NEVOD-EAS installation for the detection of extensive air showers

A new installation is dedicated to the independent evaluation of extensive air shower (EAS) energies detected in the NEVOD-DECOR experiment in the knee region of the energy spectrum. The design for the measuring system of the shower installation is based on clusters of scintillation detectors that are located on the roofs of laboratory buildings at MEPhI (Moscow) and will detect the electromagnetic (for near-vertical showers) and muon (for large zenith angles) EAS components. Features of the measuring system, the system for data acquisition and processing, and the results from investigating the characteristics of a single detector are discussed, along with the algorithm for event formation by the data of separate clusters.

Coupling functions for muon hodoscopes

The specific features of calculating the coupling functions for muon hodoscopes are considered. The results of calculating the main coupling functions for three versions of the primary spectra of cosmic rays (CR)—galactic CR, solar CR during proton events, and galactic CR variations during Forbush decreases-are presented. The calculations have been performed based on modeling CR propagation through the Earth’s atmosphere using the CORSIKA code. The mean and median CR energies, contributing to the muon detector counting rate, have been calculated for different zenith angles. It has been shown that muon detectors are sensitive to different energies of primary CRs for different directions.

Status of the NEVOD-EAS experiment

The NEVOD-EAS setup is designed for independent estimation of the EAS parameters recorded in the NEVOD-DECOR experiment in the region of the energy spectrum knee. The setup’s recording system is based on the clusters of scintillation detectors for the EAS electron-photon component, located on the territory of MEPhI. Characteristics of the shower array recording system that ensure detection, data acquisition and primary processing, and the time synchronization of clusters are discussed, along with results of studying the nonuniformity of NEVOD-EAS scintillation detector responses.

Proposal of NEVOD-EAS shower array

New setup for detection of EAS electromagnetic component at the knee region of primary energies is under construction on the basis of the experimental complex NEVOD (Moscow, Russia). The measuring system of the EAS array has a cluster organization. Clusters are located on the roofs of laboratory buildings of MEPhI (Moscow). Features of measuring and DAQ systems, results of investigations of characteristics of a single counter and the event formation algorithm from the data of separate clusters are discussed.

Observation of UHECRs in horizontal flux

Preliminary results of muon bundle studies in of zenith angle range θ ≥ 60° and multiplicities by means of coordinate detector DECOR are discussed. Estimates of muon bundle characteristics at large zenith angles obtained with CORSIKA code demonstrate the ability of such not large detector as NEVOD-DECOR complex to perform cosmic ray studies in a very wide energy range from 1011 eV to more than 1017 eV.