Energy loss measurements of inclined muon bundles in the Cherenkov water detector

An experiment on the measurements of the energy deposit of inclined cosmic ray muon bundles is being conducted at the experimental complex NEVOD (MEPhI). The complex includes the Cherenkov water calorimeter with a volume of 2000 m3 and the coordinate-tracking detector DECOR with a total area of 70 m2. The DECOR data are used to determine the local muon densities in the bundle events and their arrival directions, while the energy deposits (and hence the average muon energy loss) are evaluated from the Cherenkov calorimeter response. Average energy loss carries information about the mean muon energy in the bundles. The detection of the bundles in a wide range of muon multiplicities and zenith angles gives the opportunity to explore the energy range of primary cosmic ray particles from about 10 to 1000 PeV in the frame of a single experiment with a relatively small compact setup. Experimental results on the dependence of the muon bundle energy deposit on the zenith angle and the local muon density are presented and compared with expectations based on simulations of the EAS muon component with the CORSIKA code.

Preliminary results of the AMIGA engineering array at the Pierre Auger Observatory

The Auger Muons and Infill for the Ground Array (AMIGA) aims to both extend the detection range of the Pierre Auger Observatory down to energies ~ 1016.5 eV and to measure the muon content of extensive air showers. To accomplish these goals, its detection system is composed of an array of coupled water-Cherenkov and scintillation detectors deployed in a graded triangular grid of 433 and 750 m spacings. At each position, the scintillation detector is buried 2.3 m deep so as to shield it from the air shower electromagnetic component and thus only measure the muon component. These muon detectors have 30 m2 area split into modules, each of them highly segmented in 64 plastic-scintillator strips with an embedded wavelength-shifter optical fiber to transport light to an optical sensor located at the center of the module. During the engineering array phase (finished in November 2017) two module areas (5 m2 and 10 m2) and two optical sensors (photo-multiplier tubes and silicon-photomultipliers) were tested. In this work, we present the final performance of the muon detectors equipped with silicon-photomultipliers which were thereafter selected as the baseline design for the AMIGA production phase. Analyses and results are based both on laboratory and field measurements.