Measurement of the energy spectrum of underground muons at Gran Sasso with a transition radiation detector

TL;DR

This study directly measured the residual energy of underground cosmic ray muons at Gran Sasso using a transition radiation detector, providing data consistent with muon energy loss calculations in rock.

Contribution

First direct measurement of underground muon energy spectrum at Gran Sasso with a transition radiation detector over a two-year period.

Findings

Average muon energy is 320 GeV with statistical and systematic uncertainties.

Results agree with theoretical calculations of muon energy loss in rock.

Data covers muon energies from 100 GeV to 1 TeV.

Abstract

We have measured directly the residual energy of cosmic ray muons crossing the MACRO detector at the Gran Sasso Laboratory. For this measurement we have used a transition radiation detector consisting of three identical modules, each of about 12 m^2 area, operating in the energy region from 100 GeV to 1 TeV. The results presented here were obtained with the first module collecting data for more than two years. The average single muon energy is found to be 320 +/- 4 (stat.) +/- 11 (syst.) GeV in the rock depth range 3000-6500 hg/cm^2. The results are in agreement with calculations of the energy loss of muons in the rock above the detector.