Recent Results from the CosmoALEPH Experiment

University of Dortmund, D-44221 Dortmund, GermanyAbstract. The ALEPH detector at LEP has been supple-mented with five scintillator telescopes. This CosmoALEPHexperiment is operating at a depth of 320 m.w.e. undergroundmeasuring the muon component of extensive air showers.One aim of the experiment is to probe the chemical composi-tion of primary cosmic rays and to investigate the interactioncharacteristics of energetic protons and nuclei in the atmo-sphere in the PeV region. A first look at the cosmic ray datataken in dedicated ALEPH runs with the CosmoALEPH ex-periment shows agreement of underground muon data withgross features based on expectations from the muon contentof extensive air showers in the atmosphere.1 IntroductionThe investigation of cosmic ray muon showers in the ALEPHdetector operated at a depth of 320 meter water equivalentunderground was motivated by the observation of high mul-tiplicity events along with normal data taking of electron-positron interactions (Besier, 2000; Avati, 2000). ALEPH,which was designed as a general purpose detector for elec-troweak physicsat the Large Electron Positron collider (LEP),provides a large, sophisticated high resolution particle detec-tor to study cosmic rays underground. The ALEPH detectorwas available for cosmic ray studies in parasitic mode alongwith e