Cosmic-ray muon spectrum derived from the transferred energy spectrum of bursts observed by the mutron calorimeter

Abstract

Measurements of the energy transfer,E′, of bursts produced in a calorimeter are calibrated with the momenta of the incoming and outgoing muons measured by the Mutron magnet spectrometers. The relation between energy transferE′ and momentum difference Δpc was obtained in the energy range from 30 GeV to 1 TeV as follows:E′=(0.85±0.16) Δpc. Using this calibrated calorimeter, we observed distributions of the energy transfer of bursts produced in the calorimeter up to 6 TeV by the magnet spectrometer plus calorimeter triggers, as well as by the calorimeter trigger alone. From the observed burst spectrum, we have derived the muon energy spectrum at sea-level. The differential pion production spectrum combined with the data using composite triggers gives an exponentγ=2.58±0.19 in the muon energy region from 200 GeV to 6 TeV and 2.74±0.19 in the region from 1 TeV to 6 TeV. The muon energy spectrum thus obtained is compared with the direct measurement of the muon spectrum by the Mutron magnet spectrometers. It is thus established that measurements of the transferred energy spectrum of bursts are available for the derivation of the muon energy spectrum beyond the energy region measured by the magnet spectrometer.