V. V. Shutenko

Long-term variations in the muon flux angular distribution

The intensity of the atmospheric muon flux depends on many factors: the energy spectrum of primary cosmic rays and the state of the Earth’s heliosphere, magnetosphere, and atmosphere. The wide-aperture URAGAN muon hodoscope (Moscow, Russia, 55.7° N, 37.7° E, 173 m a.s.l.) makes it possible to investigate not only variations in the muon flux intensity but also temporal changes in the parameters of its angular distribution. These changes are analyzed using the vector of local anisotropy and its projections, which have different sensitivities to the parameters of modulation of both primary cosmic rays in the heliosphere and the Earth’s magnetosphere and secondary cosmic rays as they pass through the Earth’s atmosphere. The vector of local anisotropy is the sum of unit vectors (directions of the reconstructed muon tracks) normalized to the number of tracks. The results of an analysis of long-term variations in mean hourly projections of the vector of local anisotropy obtained from the 2007–2011 URAGAN hodoscope data 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.

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.

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.

Application of the URAGAN muon hodoscope to calibrate charged particle detectors

Independent calibration of the charged particle detectors is often required in developing different devices for elementary particle physics. The use of the URAGAN muon hodoscope, created at MEPhI’s NEVOD Scientific and Educational Center, is described. The high accuracy of muon track reconstruction allows calibration and precision study of the sensitive working volume of such detectors.

The coordinate-tracking detector based on the drift chambers for ultrahigh-energy cosmic ray investigations

The project of the tracking detector designed for a joint operation with Cherenkov water detector NEVOD and based on the drift chambers from the neutrino experiment at the IHEP accelerator U-70 is presented. The project is aimed at solving a problem called `muon puzzle — growing with energy excess of muon content in EAS in comparison with contemporary models of their development, which was registered in various experiments. Joint operation of the coordinate-tracking detector and Cherenkov water calorimeter will allow to measure energy of muon groups and to answer the question about the reasons of the muon flux excess.

Detection of muon bundles at large zenith angles

The large area coordinate detector (DECOR) represents a multilayer system of plastic streamer tube chamber modules surrounding the Cherenkov water calorimeter NEVOD. Experimental data collected during the test expositions of first. DECOR supermodules (8 vertical planes with 8.4 m 2 working area) have been analysed, angular and spatial reconstruction accuracies have been estimated. The procedure of the selection of events corresponding to detection of parallel tracks (muon bundles originated in the atmosphere) is discussed.

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.

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.

Forbush decreases recorded by the URAGAN muon hodoscope in 2006–2011

Variations in the cosmic ray muon flux on Earth’s surface during Forbush decreases (FD) recorded by the URAGAN muon hodoscope in 2006–2011 are investigated. The dependence of the rate of amplitude reduction on the primary particle energy in a range above 10 GeV at different phases of FD development is studied by analyzing the variations in the cosmic ray muon flux recorded with the hodoscope. Analytical data on the spatial and angular dynamics of the muon flux are used to estimate variations in the spatial anisotropy of the muon flux during FDs.