S. S. Khokhlov

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.

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.

Investigating the energy, angular, and temporal characteristics of forbush effects registered by the URAGAN muon hodoscope

The results from analyzing variations in the flux of cosmic ray muons during Forbush effects (FEs) registered by the URAGAN muon hodoscope over the period 2005–2009 are presented. The dependences of the amplitudes for reductions in the intensity of the cosmic ray muon flux on the energy of primary particles in energy ranges higher than 10 GeV were obtained. Their changes upon different phases of Forbush effect development were investigated. The local anisotropy vectors were calculated on the basis of spatial-angular variations in the muon flux. Correlations between the parameters of physical properties in the near heloiosphere related to the Forbush effects and the characteristics of muon flux variations were analyzed.

Project of the URAN array for registration of atmospheric neutrons

The project of a new setup is directed at the registration of atmospheric neutrons (URAN) generated by hadronic component of extensive air showers (EAS). The setup includes 72 en-detector which simultaneously register two major EAS components: electromagnetic by the group passage of charged particles and hadron component by the thermal neutrons. The neutrons and charged particles are detected using a specialized scintillation composition made of granulated alloy of crystals based on the ZnS(Ag) powder with an admixture of B2O3.

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.

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 characteristics of multi-muon events in a wide range of zenith angles

Change of the energy characteristics of muon bundles with an increase of the primary cosmic ray particles energy can be a key to solving the problem of muon excess in the extensive air showers (EAS) observed in a number of experiments. In this work the data on the energy deposit of multi-muon events in a wide range of zenith angles (and as a consequence in a wide range of primary particles energies) obtained with NEVOD-DECOR setup over a long time period are presented. The experimental data are compared with the results of simulations of EAS muon component performed using CORSIKA code.

Status of a development of the large scale coordinate-tracking setup based on the drift chambers

The large-scale coordinate detector for registration of near-horizontal muon flux of ultrahigh energy cosmic rays is being developed in MEPhI. Detector is based on the drift chambers from the neutrino experiment at the IHEP accelerator U-70, their key advantages are the large effective area (1.85 m2), good coordinate and angular resolution with a small number of measuring channels. Detector will be operated as a part of the experimental complex NEVOD, in particular, jointly with Cherenkov water detector with volume of 2000 m3. The current status of the project and results of studies of drift chamber characteristics are discussed.

Investigating the energy characteristics of muon bundles in inclined EAS

The first results from studying the energy deposits of inclined muon bundles in a Cherenkov water detector on the Earth’s surface are presented. The general response of the NEVOD Cherenkov calorimeter’s PMT is used as a measure of the energy deposited (proportional to the muon energy losses in the detector’s matter), while the local muon density at the point of observation is estimated using data from the DECOR coordinate-tracking detector. It is found that the energy deposit normalized to the muon density depends largely on the zenith angle. A comparison of the experimental results and those from EAS muon component simulations using the CORSIKA package shows that the average energy of muons detected in the bundles grows rapidly as the zenith angle increases, reaching ∼500 GeV near the horizon.