Spectrum and Charge Ratio of Vertical Cosmic Ray Muons up to Momenta of 2.5 TeV/c

The ALEPH detector at LEP has been used to measure the momentum spectrum and charge ratio of vertical cosmic ray muons underground. The sea-level cosmic ray muon spectrum for momenta up to 2.5 TeV/c has been obtained by correcting for the overburden of 320 meter water equivalent (mwe). The results are compared with Monte Carlo models for air shower development in the atmosphere. From the analysis of the spectrum the total flux and the spectral index of the cosmic ray primaries is inferred. The charge ratio suggests a dominantly light composition of cosmic ray primaries with energies up to 10^15 eV

Recent Results from the CosmoALEPH Experiment

The ALEPH detector at LEP has been supplemented with five scintillator telescopes. This CosmoALEPH experiment is operating at a depth of 320 m.w.e. under ground measuring the muon component of extensive air showers. The aim of the experiment is to look for the chemical composition of primary cosmic rays and to in vestigate the interaction characteristics of energetic protons and nuclei in the atmosphere in the PeV region. A first look at the cosmic ray data taken in dedicated runs with the CosmoALEPH experiment shows agreement of under ground muon data with gross features based on expectations from the muon content of extensive air showers in the atmosphere

Muon-pair Production by Atmospheric Muons in CosmoALEPH

Data from a dedicated cosmic ray run of the ALEPH detector were used in a study of muon trident production, i.e., muon pairs produced by muons. Here the overburden and the calorimeters are the target materials while the ALEPH time projection chamber provides the momentum measurements. A theoretical estimate of the muon trident cross section is obtained by developing a Monte Carlo simulation for muon propagation in the overburden and the detector. Two muon trident candidates were found to match the expected theoretical pattern. The observed production rate implies that the nuclear form factor cannot be neglected for muon tridents. [References: 23