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
