Cluster of scintillation counters for the shower array in the NEVOD EAS project

A shower array for investigations of primary cosmic rays in the knee region in the energy spectrum of extensive air showers is being designed on the basis of the NEVOD experimental complex. Features of the cluster organization of the array and the results of the study of the characteristics of both the basic scintillation counter and the counter cluster, which is the basic element for triggering, detecting, and data collection and treatment systems, are discussed.     

Muon calibration of the cherenkov water detector NEVOD

The problem of calibrating a Cherenkov water detector (CWD) and the possibilities for its use based on the example of the CWD NEVOD are discussed. Results of the calibration of quasi-spherical modules in water volume by means of vertical muons selected by scintillation telescopes and compared to the results from measurements performed at test facilities are presented.     

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.     

Restoration of parameters of high-energy cascades in Cherenkov water calorimeter with a dense array of quasispherical modules

A problem concerning the restoration of the parameters of a cascade shower with an unknown axis originating by muons in a Cherenkov water calorimeter is considered. A method for estimating the direction and geometric position of the cascade’s axis, which is based on the analysis of responses of quasispherical modules, and the criteria of selection of the events with cascades among the events with a large energy liberation are proposed. The method and the criteria are tested on events with cascades generated by near-horizontal muons of high energies detected by a DECOR coordinate-track detector. The preliminary results of measurements of the energy spectrum of cascade showers are presented.     

Cascade showers in the NEVOD Cherenkov water detector

A technique for measuring the cascade shower energy in the NEVOD Cherenkov water detector with a spatial lattice of quasi-spherical modules is discussed. The technique allows the number of cascade particles that move near the shower axis to be reconstructed on the basis of analysis of response amplitudes of triggered photomultiplier tubes. The technique of cascade-curve reconstruction was applied to cascade showers generated by near-horizontal high-energy muons extracted by means of the DECOR coordinate-tracking detector arranged around the Cherenkov water detector. The first results of measuring the energy spectrum of cascade showers of 10–1000 GeV are presented.     

NEVOD–DECOR Experiment on the Measurement of the Energy Deposit of Cosmic Ray Muon Bundles

Physics of Atomic Nuclei - In comparison with calculations, the excess of multimuon events found in many experiments at ultrahigh energies of extensive air showers (EASs) cannot be explained using...     

Study of cascade showers generated by near-horizontal muons in the water Cherenkov detector with a dense array of optical modules

The method for reconstructing the cascade curve by the Cherenkov radiation in water of the NEVOD detector with a dense spatial array of optical modules is discussed. Cascades are generated by near-horizontal muons which are separated by the DECOR coordinate detector. The cascade curves and the cascade energy spectrum measured in an ～8000-hour measurement series are presented.     

New detecting system of the NEVOD Cherenkov water detector

A new detecting system of the NEVOD Cherenkov water detector is described, whose development implies replacement of photomultipliers in quasispherical modules of the existing three-dimensional network by low-noise FEU-200 photomultipliers, their dynamic range expansion with the purpose to study events with energies above 10¹⁷ eV, the transition to the cluster structure principle, and the possibility of operating in the hodoscopic mode.     

Investigation of the Energy Loss of Muon Bundles in the Cherenkov Water Calorimeter

Investigations of the energy loss of muon bundles are being conducted at the Experimental complex NEVOD. Such investigations are directed to detailed study of “muon puzzle” (the excess of multi-muon events observed in several cosmic ray experiments at ultra-high energies). Results of measurements of the muon bundle energy deposit during a long period of observations in primary cosmic ray energy range 10–1000 PeV have been obtained and have been compared with simulations performed on the basis of the CORSIKA code.     

Spatial distribution of Cherenkov light from cascade showers in water

The spatial distribution of the Cherenkov light generated by cascade showers is analyzed using the NEVOD Cherenkov water detector. The dependence of the Cherenkov light intensity on the depth of shower development at various distances from the shower axis is investigated for the first time. The experimental data are compared with the Cherenkov light distributions predicted by various models for the scattering of cascade particles.