Measurements of the energy deposit of multi-muon events in the Cherenkov water calorimeter

R.P Kokoulin,I.I Yashin,S.S Khokhlov,G Trinchero,K.G Kompaniets,A.A Petrukhin,V.V Kindin,N.S Barbashina,V.V Shutenko,A.G Bogdanov,O Saavedra,V.A Khomyakov,D.V Chernov,L.I Dushkin,E.A Yurina,G Mannocchi,B Pattison

doi:10.1051/epjconf/201714516002

Abstract

To solve the problem of the excess of multi-muon events observed in several cosmic ray experiments at ultra-high energies (so-called “muon puzzle”), an analysis of the energy characteristics of the muon component of extensive air showers (EAS) is required. A possible approach to such investigations is the measurement of the energy deposit of muon bundles in the detector, which provides information on the mean muon energy. In the experiment now being conducted at the NEVOD-DECOR complex, the local muon density and EAS arrival direction are determined according to the data of the coordinate-tracking detector DECOR, whereas the energy deposit is measured by means of the Cherenkov water calorimeter NEVOD. Results of the measurements of the energy deposit of inclined muon bundles based on the data accumulated during more than 23,200 h observations in 2012 – 2016 are presented and compared with simulations performed by means of the CORSIKA code.

Highlights

High rates of high-multiplicity muon bundle events were found in cosmic ray experiments conducted at the LEP detectors ALEPH [1] and DELPHI [2]
The analysis of the DECOR data [3, 4] on inclined muon bundles with a high multiplicity at large zenith angles showed that the measured event intensity cannot be explained in the frame of the existing hadron interaction models even under the assumption of an extremely heavy mass composition at primary energies around 1018 eV
The Cherenkov water detector (CWD) NEVOD [8] has an inner volume of 9 × 9 × 26 cubic meters and is equipped with a spatial lattice of quasi-spherical measuring modules (QSM)

Summary

Introduction

High rates of high-multiplicity muon bundle events were found in cosmic ray experiments conducted at the LEP detectors ALEPH [1] and DELPHI [2]. At that time, it was interpreted as an indication for a heavy mass composition at very high primary particle energies. The analysis of the DECOR data [3, 4] on inclined muon bundles with a high multiplicity at large zenith angles showed that the measured event intensity cannot be explained in the frame of the existing hadron interaction models even under the assumption of an extremely heavy (pure iron nuclei) mass composition at primary energies around 1018 eV. The inconsistant muon abundance in EAS at ultra-high energies is often referred to as the “muon problem” or “muon puzzle”

Experimental data

Results and discussion

Conclusion